# PGPLOT Subroutine Descriptions

## Introduction

This appendix includes a list of all the PGPLOT subroutines, and then gives detailed instructions for the use of each routine in Fortran programs. The subroutine descriptions are in alphabetical order.

## Arguments

The subroutine descriptions indicate the data type of each argument. When arguments are described as ``input'', they may be replaced with constants or expressions in the `CALL` statement, but make sure that the constant or expression has the correct data type.

`INTEGER` arguments:
  these should be declared `INTEGER` or `INTEGER*4` in the calling program, not `INTEGER*2`.
`REAL` arguments:
  these should be declared `REAL` or `REAL*4` in the calling program, not `REAL*8` or `DOUBLE PRECISION`.
`LOGICAL` arguments:
  these should be declared `LOGICAL` or `LOGICAL*4` in the calling program.
`CHARACTER` arguments:
  any valid Fortran `CHARACTER` variable may be used (declared `CHARACTER*n` for some integer `n`).

## Index of Routines

Version 5.2

- PGADVANCE -- non-standard alias for PGPAGE
- PGARRO -- draw an arrow
- PGASK -- control new page prompting
- PGAXIS -- draw an axis
- PGBAND -- read cursor position, with anchor
- PGBBUF -- begin batch of output (buffer)
- PGBEG -- open a graphics device
- PGBEGIN -- non-standard alias for PGBEG
- PGBIN -- histogram of binned data
- PGBOX -- draw labeled frame around viewport
- PGCIRC -- draw a circle, using fill-area attributes
- PGCLOS -- close the selected graphics device
- PGCONB -- contour map of a 2D data array, with blanking
- PGCONF -- fill between two contours
- PGCONL -- label contour map of a 2D data array
- PGCONS -- contour map of a 2D data array (fast algorithm)
- PGCONT -- contour map of a 2D data array (contour-following)
- PGCONX -- contour map of a 2D data array (non rectangular)
- PGCTAB -- install the color table to be used by PGIMAG
- PGCURS -- read cursor position
- PGCURSE -- non-standard alias for PGCURS
- PGDRAW -- draw a line from the current pen position to a point
- PGEBUF -- end batch of output (buffer)
- PGEND -- close all open graphics devices
- PGENV -- set window and viewport and draw labeled frame
- PGERAS -- erase all graphics from current page
- PGERR1 -- horizontal or vertical error bar
- PGERRB -- horizontal or vertical error bar
- PGERRX -- horizontal error bar
- PGERRY -- vertical error bar
- PGETXT -- erase text from graphics display
- PGFUNT -- function defined by X = F(T), Y = G(T)
- PGFUNX -- function defined by Y = F(X)
- PGFUNY -- function defined by X = F(Y)
- PGGRAY -- gray-scale map of a 2D data array
- PGHI2D -- cross-sections through a 2D data array
- PGHIST -- histogram of unbinned data
- PGIDEN -- write username, date, and time at bottom of plot
- PGIMAG -- color image from a 2D data array
- PGLAB -- write labels for x-axis, y-axis, and top of plot
- PGLABEL -- non-standard alias for PGLAB
- PGLCUR -- draw a line using the cursor
- PGLDEV -- list available device types on standard output
- PGLEN -- find length of a string in a variety of units
- PGLINE -- draw a polyline (curve defined by line-segments)
- PGMOVE -- move pen (change current pen position)
- PGMTEXT -- non-standard alias for PGMTXT
- PGMTXT -- write text at position relative to viewport
- PGNCUR -- mark a set of points using the cursor
- PGNCURSE -- non-standard alias for PGNCUR
- PGNUMB -- convert a number into a plottable character string
- PGOLIN -- mark a set of points using the cursor
- PGOPEN -- open a graphics device
- PGPAGE -- advance to new page
- PGPANL -- switch to a different panel on the view surface
- PGPAP -- change the size of the view surface
- PGPAPER -- non-standard alias for PGPAP
- PGPIXL -- draw pixels
- PGPNTS -- draw several graph markers, not all the same
- PGPOINT -- non-standard alias for PGPT
- PGPOLY -- draw a polygon, using fill-area attributes
- PGPT -- draw several graph markers
- PGPT1 -- draw one graph marker
- PGPTEXT -- non-standard alias for PGPTXT
- PGPTXT -- write text at arbitrary position and angle
- PGQAH -- inquire arrow-head style
- PGQCF -- inquire character font
- PGQCH -- inquire character height
- PGQCI -- inquire color index
- PGQCIR -- inquire color index range
- PGQCLP -- inquire clipping status
- PGQCOL -- inquire color capability
- PGQCR -- inquire color representation
- PGQCS -- inquire character height in a variety of units
- PGQDT -- inquire name of nth available device type
- PGQFS -- inquire fill-area style
- PGQHS -- inquire hatching style
- PGQID -- inquire current device identifier
- PGQINF -- inquire PGPLOT general information
- PGQITF -- inquire image transfer function
- PGQLS -- inquire line style
- PGQLW -- inquire line width
- PGQNDT -- inquire number of available device types
- PGQPOS -- inquire current pen position
- PGQTBG -- inquire text background color index
- PGQTXT -- find bounding box of text string
- PGQVP -- inquire viewport size and position
- PGQVSZ -- inquire size of view surface
- PGQWIN -- inquire window boundary coordinates
- PGRECT -- draw a rectangle, using fill-area attributes
- PGRND -- find the smallest `round' number greater than x
- PGRNGE -- choose axis limits
- PGSAH -- set arrow-head style
- PGSAVE -- save PGPLOT attributes
- PGUNSA -- restore PGPLOT attributes
- PGSCF -- set character font
- PGSCH -- set character height
- PGSCI -- set color index
- PGSCIR -- set color index range
- PGSCLP -- enable or disable clipping at edge of viewport
- PGSCR -- set color representation
- PGSCRL -- scroll window
- PGSCRN -- set color representation by name
- PGSFS -- set fill-area style
- PGSHLS -- set color representation using HLS system
- PGSHS -- set hatching style
- PGSITF -- set image transfer function
- PGSLCT -- select an open graphics device
- PGSLS -- set line style
- PGSLW -- set line width
- PGSTBG -- set text background color index
- PGSUBP -- subdivide view surface into panels
- PGSVP -- set viewport (normalized device coordinates)
- PGSWIN -- set window
- PGTBOX -- draw frame and write (DD) HH MM SS.S labelling
- PGTEXT -- write text (horizontal, left-justified)
- PGTICK -- draw a single tick mark on an axis
- PGUPDT -- update display
- PGVECT -- vector map of a 2D data array, with blanking
- PGVPORT -- non-standard alias for PGSVP
- PGVSIZ -- set viewport (inches)
- PGVSIZE -- non-standard alias for PGVSIZ
- PGVSTAND -- non-standard alias for PGVSTD
- PGVSTD -- set standard (default) viewport
- PGWEDG -- annotate an image plot with a wedge
- PGWINDOW -- non-standard alias for PGSWIN
- PGWNAD -- set window and adjust viewport to same aspect ratio

## PGADVANCE -- non-standard alias for PGPAGE

          SUBROUTINE PGADVANCE

    See description of PGPAGE.

## PGARRO -- draw an arrow

          SUBROUTINE PGARRO (X1, Y1, X2, Y2)
          REAL X1, Y1, X2, Y2

    Draw an arrow from the point with world-coordinates (X1,Y1) to
    (X2,Y2). The size of the arrowhead at (X2,Y2) is determined by
    the current character size set by routine PGSCH. The default size
    is 1/40th of the smaller of the width or height of the view surface.
    The appearance of the arrowhead (shape and solid or open) is
    controlled by routine PGSAH.

    Arguments:
     X1, Y1 (input)  : world coordinates of the tail of the arrow.
     X2, Y2 (input)  : world coordinates of the head of the arrow.

## PGASK -- control new page prompting

          SUBROUTINE PGASK (FLAG)
          LOGICAL FLAG

    Change the ``prompt state'' of PGPLOT. If the prompt state is
    ON, PGPAGE will type ``Type RETURN for next page:'' and will wait
    for the user to type a carriage-return before starting a new page.
    The initial prompt state (after the device has been opened) is ON
    for interactive devices. Prompt state is always OFF for
    non-interactive devices.

    Arguments:
     FLAG   (input)  : if .TRUE., and if the device is an interactive
                       device, the prompt state will be set to ON. If
                       .FALSE., the prompt state will be set to OFF.

## PGAXIS -- draw an axis

          SUBROUTINE PGAXIS (OPT, X1, Y1, X2, Y2, V1, V2, STEP, NSUB,
         :                   DMAJL, DMAJR, FMIN, DISP, ORIENT)
          CHARACTER*(*) OPT
          REAL X1, Y1, X2, Y2, V1, V2, STEP, DMAJL, DMAJR, FMIN, DISP
          REAL ORIENT
          INTEGER NSUB

    Draw a labelled graph axis from world-coordinate position (X1,Y1) to
    (X2,Y2).

    Normally, this routine draws a standard LINEAR axis with equal
    subdivisions.   The quantity described by the axis runs from V1 to V2;
    this may be, but need not be, the same as X or Y.

    If the 'L' option is specified, the routine draws a LOGARITHMIC axis.
    In this case, the quantity described by the axis runs from 10**V1 to
    10**V2. A logarithmic axis always has major, labeled, tick marks
    spaced by one or more decades. If the major tick marks are spaced
    by one decade (as specified by the STEP argument), then minor
    tick marks are placed at 2, 3, .., 9 times each power of 10;
    otherwise minor tick marks are spaced by one decade. If the axis
    spans less than two decades, numeric labels are placed at 1, 2, and
    5 times each power of ten.

    If the axis spans less than one decade, or if it spans many decades,
    it is preferable to use a linear axis labeled with the logarithm of
    the quantity of interest.

    Arguments:
     OPT    (input)  : a string containing single-letter codes for
                       various options. The options currently
                       recognized are:
                       L : draw a logarithmic axis
                       N : write numeric labels
                       1 : force decimal labelling, instead of automatic
                           choice (see PGNUMB).
                       2 : force exponential labelling, instead of
                           automatic.
     X1, Y1 (input)  : world coordinates of one endpoint of the axis.
     X2, Y2 (input)  : world coordinates of the other endpoint of the axis.
     V1     (input)  : axis value at first endpoint.
     V2     (input)  : axis value at second endpoint.
     STEP   (input)  : major tick marks are drawn at axis value 0.0 plus
                       or minus integer multiples of STEP. If STEP=0.0,
                       a value is chosen automatically.
     NSUB   (input)  : minor tick marks are drawn to divide the major
                       divisions into NSUB equal subdivisions (ignored if
                       STEP=0.0). If NSUB <= 1, no minor tick marks are
                       drawn. NSUB is ignored for a logarithmic axis.
     DMAJL  (input)  : length of major tick marks drawn to left of axis
                       (as seen looking from first endpoint to second), in
                       units of the character height.
     DMAJR  (input)  : length of major tick marks drawn to right of axis,
                       in units of the character height.
     FMIN   (input)  : length of minor tick marks, as fraction of major.
     DISP   (input)  : displacement of baseline of tick labels to
                       right of axis, in units of the character height.
     ORIENT (input)  : orientation of label text, in degrees; angle between
                       baseline of text and direction of axis (0-360°).

## PGBAND -- read cursor position, with anchor

          INTEGER FUNCTION PGBAND (MODE, POSN, XREF, YREF, X, Y, CH)
          INTEGER MODE, POSN
          REAL XREF, YREF, X, Y
          CHARACTER*(*) CH

    Read the cursor position and a character typed by the user.
    The position is returned in world coordinates.  PGBAND positions
    the cursor at the position specified (if POSN=1), allows the user to
    move the cursor using the mouse or arrow keys or whatever is available
    on the device. When he has positioned the cursor, the user types a
    single character on the keyboard; PGBAND then returns this
    character and the new cursor position (in world coordinates).

    Some interactive devices offer a selection of cursor types,
    implemented as thin lines that move with the cursor, but without
    erasing underlying graphics. Of these types, some extend between
    a stationary anchor-point at XREF,YREF, and the position of the
    cursor, while others simply follow the cursor without changing shape
    or size. The cursor type is specified with one of the following MODE
    values. Cursor types that are not supported by a given device, are
    treated as MODE=0.

    -- If MODE=0, the anchor point is ignored and the routine behaves
    like PGCURS.
    -- If MODE=1, a straight line is drawn joining the anchor point
    and the cursor position.
    -- If MODE=2, a hollow rectangle is extended as the cursor is moved,
    with one vertex at the anchor point and the opposite vertex at the
    current cursor position; the edges of the rectangle are horizontal
    and vertical.
    -- If MODE=3, two horizontal lines are extended across the width of
    the display, one drawn through the anchor point and the other
    through the moving cursor position. This could be used to select
    a Y-axis range when one end of the range is known.
    -- If MODE=4, two vertical lines are extended over the height of
    the display, one drawn through the anchor point and the other
    through the moving cursor position. This could be used to select an
    X-axis range when one end of the range is known.
    -- If MODE=5, a horizontal line is extended through the cursor
    position over the width of the display. This could be used to select
    an X-axis value such as the start of an X-axis range. The anchor point
    is ignored.
    -- If MODE=6, a vertical line is extended through the cursor
    position over the height of the display. This could be used to select
    a Y-axis value such as the start of a Y-axis range. The anchor point
    is ignored.
    -- If MODE=7, a cross-hair, centered on the cursor, is extended over
    the width and height of the display. The anchor point is ignored.

    Returns:
     PGBAND          : 1 if the call was successful; 0 if the device
                       has no cursor or some other error occurs.
    Arguments:
     MODE   (input)  : display mode (0, 1, ..7: see above).
     POSN   (input)  : if POSN=1, PGBAND attempts to place the cursor
                       at point (X,Y); if POSN=0, it leaves the cursor
                       at its current position. (On some devices this
                       request may be ignored.)
     XREF   (input)  : the world x-coordinate of the anchor point.
     YREF   (input)  : the world y-coordinate of the anchor point.
     X      (in/out) : the world x-coordinate of the cursor.
     Y      (in/out) : the world y-coordinate of the cursor.
     CH     (output) : the character typed by the user; if the device has
                       no cursor or if some other error occurs, the value
                       CHAR(0) [ASCII NUL character] is returned.

    Note: The cursor coordinates (X,Y) may be changed by PGBAND even if
    the device has no cursor or if the user does not move the cursor.
    Under these circumstances, the position returned in (X,Y) is that of
    the pixel nearest to the requested position.

## PGBBUF -- begin batch of output (buffer)

          SUBROUTINE PGBBUF

    Begin saving graphical output commands in an internal buffer; the
    commands are held until a matching PGEBUF call (or until the buffer
    is emptied by PGUPDT). This can greatly improve the efficiency of
    PGPLOT.  PGBBUF increments an internal counter, while PGEBUF
    decrements this counter and flushes the buffer to the output
    device when the counter drops to zero.  PGBBUF and PGEBUF calls
    should always be paired.

    Arguments: none

## PGBEG -- open a graphics device

          INTEGER FUNCTION PGBEG (UNIT, FILE, NXSUB, NYSUB)
          INTEGER       UNIT
          CHARACTER*(*) FILE
          INTEGER       NXSUB, NYSUB

    Note: new programs should use PGOPEN rather than PGBEG. PGOPEN
    is retained for compatibility with existing programs. Unlike PGOPEN,
    PGBEG closes any graphics devices that are already open, so it
    cannot be used to open devices to be used in parallel.

    PGBEG opens a graphical device or file and prepares it for
    subsequent plotting. A device must be opened with PGBEG or PGOPEN
    before any other calls to PGPLOT subroutines for the device.

    If any device  is already open for PGPLOT output, it is closed before
    the new device is opened.

    Returns:
     PGBEG         : a status return value. A value of 1 indicates
                       successful completion, any other value indicates
                       an error. In the event of error a message is
                       written on the standard error unit.
                       To test the return value, call
                       PGBEG as a function, eg IER=PGBEG(...); note
                       that PGBEG must be declared INTEGER in the
                       calling program. Some Fortran compilers allow
                       you to use CALL PGBEG(...) and discard the
                       return value, but this is not standard Fortran.
    Arguments:
     UNIT  (input)   : this argument is ignored by PGBEG (use zero).
     FILE  (input)   : the "device specification" for the plot device.
                       (For explanation, see description of PGOPEN.)
     NXSUB  (input)  : the number of subdivisions of the view surface in
                       X (>0 or <0).
     NYSUB  (input)  : the number of subdivisions of the view surface in
                       Y (>0).
                       PGPLOT puts NXSUB x NYSUB graphs on each plot
                       page or screen; when the view surface is sub-
                       divided in this way, PGPAGE moves to the next
                       panel, not the  next physical page. If
                       NXSUB > 0, PGPLOT uses the panels in row
                       order; if <0, PGPLOT uses them in column order.

## PGBEGIN -- non-standard alias for PGBEG

          INTEGER FUNCTION PGBEGIN (UNIT, FILE, NXSUB, NYSUB)
          INTEGER       UNIT
          CHARACTER*(*) FILE
          INTEGER       NXSUB, NYSUB

    See description of PGBEG.

## PGBIN -- histogram of binned data

          SUBROUTINE PGBIN (NBIN, X, DATA, CENTER)
          INTEGER NBIN
          REAL X(*), DATA(*)
          LOGICAL CENTER

    Plot a histogram of NBIN values with X(1..NBIN) values along
    the ordinate, and DATA(1...NBIN) along the abscissa. Bin width is
    spacing between X values.

    Arguments:
     NBIN   (input)  : number of values.
     X      (input)  : abscissae of bins.
     DATA   (input)  : data values of bins.
     CENTER (input)  : if .TRUE., the X values denote the center of the
                       bin; if .FALSE., the X values denote the lower
                       edge (in X) of the bin.

## PGBOX -- draw labeled frame around viewport

          SUBROUTINE PGBOX (XOPT, XTICK, NXSUB, YOPT, YTICK, NYSUB)
          CHARACTER*(*) XOPT, YOPT
          REAL XTICK, YTICK
          INTEGER NXSUB, NYSUB

    Annotate the viewport with frame, axes, numeric labels, etc.
    PGBOX is called by on the user's behalf by PGENV, but may also be
    called explicitly.

    Arguments:
     XOPT   (input)  : string of options for X (horizontal) axis of
                       plot. Options are single letters, and may be in
                       any order (see below).
     XTICK  (input)  : world coordinate interval between major tick marks
                       on X axis. If XTICK=0.0, the interval is chosen by
                       PGBOX, so that there will be at least 3 major tick
                       marks along the axis.
     NXSUB  (input)  : the number of subintervals to divide the major
                       coordinate interval into. If XTICK=0.0 or NXSUB=0,
                       the number is chosen by PGBOX.
     YOPT   (input)  : string of options for Y (vertical) axis of plot.
                       Coding is the same as for XOPT.
     YTICK  (input)  : like XTICK for the Y axis.
     NYSUB  (input)  : like NXSUB for the Y axis.

    Options (for parameters XOPT and YOPT):
     A : draw Axis (X axis is horizontal line Y=0, Y axis is vertical
         line X=0).
     B : draw bottom (X) or left (Y) edge of frame.
     C : draw top (X) or right (Y) edge of frame.
     G : draw Grid of vertical (X) or horizontal (Y) lines.
     I : Invert the tick marks; ie draw them outside the viewport
         instead of inside.
     L : label axis Logarithmically (see below).
     N : write Numeric labels in the conventional location below the
         viewport (X) or to the left of the viewport (Y).
     P : extend ("Project") major tick marks outside the box (ignored if
         option I is specified).
     M : write numeric labels in the unconventional location above the
         viewport (X) or to the right of the viewport (Y).
     T : draw major Tick marks at the major coordinate interval.
     S : draw minor tick marks (Subticks).
     V : orient numeric labels Vertically. This is only applicable to Y.
         The default is to write Y-labels parallel to the axis.
     1 : force decimal labelling, instead of automatic choice (see PGNUMB).
     2 : force exponential labelling, instead of automatic.

    To get a complete frame, specify BC in both XOPT and YOPT.
    Tick marks, if requested, are drawn on the axes or frame
    or both, depending which are requested. If none of ABC is specified,
    tick marks will not be drawn. When PGENV calls PGBOX, it sets both
    XOPT and YOPT according to the value of its parameter AXIS:
    -1: 'BC', 0: 'BCNST', 1: 'ABCNST', 2: 'ABCGNST'.

    For a logarithmic axis, the major tick interval is always 1.0. The
    numeric label is 10**(x) where x is the world coordinate at the
    tick mark. If subticks are requested, 8 subticks are drawn between
    each major tick at equal logarithmic intervals.

    To label an axis with time (days, hours, minutes, seconds) or
    angle (degrees, arcmin, arcsec), use routine PGTBOX.

## PGCIRC -- draw a circle, using fill-area attributes

          SUBROUTINE PGCIRC (XCENT, YCENT, RADIUS)
          REAL XCENT, YCENT, RADIUS

    Draw a circle. The action of this routine depends
    on the setting of the Fill-Area Style attribute. If Fill-Area Style
    is SOLID (the default), the interior of the circle is solid-filled
    using the current Color Index. If Fill-Area Style is HOLLOW, the
    outline of the circle is drawn using the current line attributes
    (color index, line-style, and line-width).

    Arguments:
     XCENT  (input)  : world x-coordinate of the center of the circle.
     YCENT  (input)  : world y-coordinate of the center of the circle.
     RADIUS (input)  : radius of circle (world coordinates).

## PGCLOS -- close the selected graphics device

          SUBROUTINE PGCLOS

    Close the currently selected graphics device. After the device has
    been closed, either another open device must be selected with PGSLCT
    or another device must be opened with PGOPEN before any further
    plotting can be done. If the call to PGCLOS is omitted, some or all
    of the plot may be lost.

    [This routine was added to PGPLOT in Version 5.1.0. Older programs
    use PGEND instead.]

    Arguments: none

## PGCONB -- contour map of a 2D data array, with blanking

          SUBROUTINE PGCONB (A, IDIM, JDIM, I1, I2, J1, J2, C, NC, TR,
         1                   BLANK)
          INTEGER IDIM, JDIM, I1, I2, J1, J2, NC
          REAL    A(IDIM,JDIM), C(*), TR(6), BLANK

    Draw a contour map of an array. This routine is the same as PGCONS,
    except that array elements that have the "magic value" defined by
    argument BLANK are ignored, making gaps in the contour map. The
    routine may be useful for data measured on most but not all of the
    points of a grid.

    Arguments:
     A      (input)  : data array.
     IDIM   (input)  : first dimension of A.
     JDIM   (input)  : second dimension of A.
     I1,I2  (input)  : range of first index to be contoured (inclusive).
     J1,J2  (input)  : range of second index to be contoured (inclusive).
     C      (input)  : array of contour levels (in the same units as the
                       data in array A); dimension at least NC.
     NC     (input)  : number of contour levels (less than or equal to
                       dimension of C). The absolute value of this
                       argument is used (for compatibility with PGCONT,
                       where the sign of NC is significant).
     TR     (input)  : array defining a transformation between the I,J
                       grid of the array and the world coordinates. The
                       world coordinates of the array point A(I,J) are
                       given by:
                         X = TR(1) + TR(2)*I + TR(3)*J
                         Y = TR(4) + TR(5)*I + TR(6)*J
                       Usually TR(3) and TR(5) are zero - unless the
                       coordinate transformation involves a rotation
                       or shear.
     BLANK   (input) : elements of array A that are exactly equal to
                       this value are ignored (blanked).

## PGCONF -- fill between two contours

          SUBROUTINE PGCONF (A, IDIM, JDIM, I1, I2, J1, J2, C1, C2, TR)
          INTEGER IDIM, JDIM, I1, I2, J1, J2
          REAL    A(IDIM,JDIM), C1, C2, TR(6)

    Shade the region between two contour levels of a function defined on
    the nodes of a rectangular grid. The routine uses the current fill
    attributes, hatching style (if appropriate), and color index.

    If you want to both shade between contours and draw the contour
    lines, call this routine first (once for each pair of levels) and
    then CALL PGCONT (or PGCONS) to draw the contour lines on top of the
    shading.

    Note 1: This routine is not very efficient: it generates a polygon
    fill command for each cell of the mesh that intersects the desired
    area, rather than consolidating adjacent cells into a single polygon.

    Note 2: If both contours intersect all four edges of a particular
    mesh cell, the program behaves badly and may consider some parts
    of the cell to lie in more than one contour range.

    Note 3: If a contour crosses all four edges of a cell, this
    routine may not generate the same contours as PGCONT or PGCONS
    (these two routines may not agree either). Such cases are always
    ambiguous and the routines use different approaches to resolving
    the ambiguity.

    Arguments:
     A      (input)  : data array.
     IDIM   (input)  : first dimension of A.
     JDIM   (input)  : second dimension of A.
     I1,I2  (input)  : range of first index to be contoured (inclusive).
     J1,J2  (input)  : range of second index to be contoured (inclusive).
     C1, C2 (input)  : contour levels; note that C1 must be less than C2.
     TR     (input)  : array defining a transformation between the I,J
                       grid of the array and the world coordinates. The
                       world coordinates of the array point A(I,J) are
                       given by:
                         X = TR(1) + TR(2)*I + TR(3)*J
                         Y = TR(4) + TR(5)*I + TR(6)*J
                       Usually TR(3) and TR(5) are zero - unless the
                       coordinate transformation involves a rotation
                       or shear.

## PGCONL -- label contour map of a 2D data array

          SUBROUTINE PGCONL (A, IDIM, JDIM, I1, I2, J1, J2, C, TR,
         1                   LABEL, INTVAL, MININT)
          INTEGER IDIM, JDIM, I1, J1, I2, J2, INTVAL, MININT
          REAL A(IDIM,JDIM), C, TR(6)
          CHARACTER*(*) LABEL

    Label a contour map drawn with routine PGCONT. Routine PGCONT should
    be called first to draw the contour lines, then this routine should be
    called to add the labels. Labels are written at intervals along the
    contour lines, centered on the contour lines with lettering aligned
    in the up-hill direction. Labels are opaque, so a part of the under-
    lying contour line is obscured by the label. Labels use the current
    attributes (character height, line width, color index, character
    font).

    The first 9 arguments are the same as those supplied to PGCONT, and
    should normally be identical to those used with PGCONT. Note that
    only one contour level can be specified; tolabel more contours, call
    PGCONL for each level.

    The Label is supplied as a character string in argument LABEL.

    The spacing of labels along the contour is specified by parameters
    INTVAL and MININT. The routine follows the contour through the
    array, counting the number of cells that the contour crosses. The
    first label will be written in the MININT'th cell, and additional
    labels will be written every INTVAL cells thereafter. A contour
    that crosses less than MININT cells will not be labelled. Some
    experimentation may be needed to get satisfactory results; a good
    place to start is INTVAL=20, MININT=10.

    Arguments:
     A      (input) : data array.
     IDIM   (input) : first dimension of A.
     JDIM   (input) : second dimension of A.
     I1, I2 (input) : range of first index to be contoured (inclusive).
     J1, J2 (input) : range of second index to be contoured (inclusive).
     C      (input) : the level of the contour to be labelled (one of the
                      values given to PGCONT).
     TR     (input) : array defining a transformation between the I,J
                      grid of the array and the world coordinates.
                      The world coordinates of the array point A(I,J)
                      are given by:
                        X = TR(1) + TR(2)*I + TR(3)*J
                        Y = TR(4) + TR(5)*I + TR(6)*J
                      Usually TR(3) and TR(5) are zero - unless the
                      coordinate transformation involves a rotation or
                      shear.
     LABEL  (input) : character strings to be used to label the specified
                      contour. Leading and trailing blank spaces are
                      ignored.
     INTVAL (input) : spacing along the contour between labels, in
                      grid cells.
     MININT (input) : contours that cross less than MININT cells
                      will not be labelled.

## PGCONS -- contour map of a 2D data array (fast algorithm)

          SUBROUTINE PGCONS (A, IDIM, JDIM, I1, I2, J1, J2, C, NC, TR)
          INTEGER IDIM, JDIM, I1, I2, J1, J2, NC
          REAL    A(IDIM,JDIM), C(*), TR(6)

    Draw a contour map of an array. The map is truncated if
    necessary at the boundaries of the viewport.  Each contour line is
    drawn with the current line attributes (color index, style, and
    width).  This routine, unlike PGCONT, does not draw each contour as a
    continuous line, but draws the straight line segments composing each
    contour in a random order.  It is thus not suitable for use on pen
    plotters, and it usually gives unsatisfactory results with dashed or
    dotted lines.  It is, however, faster than PGCONT, especially if
    several contour levels are drawn with one call of PGCONS.

    Arguments:
     A      (input)  : data array.
     IDIM   (input)  : first dimension of A.
     JDIM   (input)  : second dimension of A.
     I1,I2  (input)  : range of first index to be contoured (inclusive).
     J1,J2  (input)  : range of second index to be contoured (inclusive).
     C      (input)  : array of contour levels (in the same units as the
                       data in array A); dimension at least NC.
     NC     (input)  : number of contour levels (less than or equal to
                       dimension of C). The absolute value of this
                       argument is used (for compatibility with PGCONT,
                       where the sign of NC is significant).
     TR     (input)  : array defining a transformation between the I,J
                       grid of the array and the world coordinates. The
                       world coordinates of the array point A(I,J) are
                       given by:
                         X = TR(1) + TR(2)*I + TR(3)*J
                         Y = TR(4) + TR(5)*I + TR(6)*J
                       Usually TR(3) and TR(5) are zero - unless the
                       coordinate transformation involves a rotation
                       or shear.

## PGCONT -- contour map of a 2D data array (contour-following)

          SUBROUTINE PGCONT (A, IDIM, JDIM, I1, I2, J1, J2, C, NC, TR)
          INTEGER IDIM, JDIM, I1, J1, I2, J2, NC
          REAL A(IDIM,JDIM), C(*), TR(6)

    Draw a contour map of an array.  The map is truncated if
    necessary at the boundaries of the viewport.  Each contour line
    is drawn with the current line attributes (color index, style, and
    width); except that if argument NC is positive (see below), the line
    style is set by PGCONT to 1 (solid) for positive contours or 2
    (dashed) for negative contours.

    Arguments:
     A      (input) : data array.
     IDIM   (input) : first dimension of A.
     JDIM   (input) : second dimension of A.
     I1, I2 (input) : range of first index to be contoured (inclusive).
     J1, J2 (input) : range of second index to be contoured (inclusive).
     C      (input) : array of NC contour levels; dimension at least NC.
     NC     (input) : +/- number of contour levels (less than or equal
                      to dimension of C). If NC is positive, it is the
                      number of contour levels, and the line-style is
                      chosen automatically as described above. If NC is
                      negative, it is minus the number of contour
                      levels, and the current setting of line-style is
                      used for all the contours.
     TR     (input) : array defining a transformation between the I,J
                      grid of the array and the world coordinates.
                      The world coordinates of the array point A(I,J)
                      are given by:
                        X = TR(1) + TR(2)*I + TR(3)*J
                        Y = TR(4) + TR(5)*I + TR(6)*J
                      Usually TR(3) and TR(5) are zero - unless the
                      coordinate transformation involves a rotation or
                      shear.

## PGCONX -- contour map of a 2D data array (non rectangular)

          SUBROUTINE PGCONX (A, IDIM, JDIM, I1, I2, J1, J2, C, NC, PLOT)
          INTEGER  IDIM, JDIM, I1, J1, I2, J2, NC
          REAL     A(IDIM,JDIM), C(*)
          EXTERNAL PLOT

    Draw a contour map of an array using a user-supplied plotting
    routine.  This routine should be used instead of PGCONT when the
    data are defined on a non-rectangular grid.  PGCONT permits only
    a linear transformation between the (I,J) grid of the array
    and the world coordinate system (x,y), but PGCONX permits any
    transformation to be used, the transformation being defined by a
    user-supplied subroutine. The nature of the contouring algorithm,
    however, dictates that the transformation should maintain the
    rectangular topology of the grid, although grid-points may be
    allowed to coalesce.  As an example of a deformed rectangular
    grid, consider data given on the polar grid theta=0.1n(pi/2),
    for n=0,1,...,10, and r=0.25m, for m=0,1,..,4. This grid
    contains 55 points, of which 11 are coincident at the origin.
    The input array for PGCONX should be dimensioned (11,5), and
    data values should be provided for all 55 elements.  PGCONX can
    also be used for special applications in which the height of the
    contour affects its appearance, e.g., stereoscopic views.

    The map is truncated if necessary at the boundaries of the viewport.
    Each contour line is drawn with the current line attributes (color
    index, style, and width); except that if argument NC is positive
    (see below), the line style is set by PGCONX to 1 (solid) for
    positive contours or 2 (dashed) for negative contours. Attributes
    for the contour lines can also be set in the user-supplied
    subroutine, if desired.

    Arguments:
     A      (input) : data array.
     IDIM   (input) : first dimension of A.
     JDIM   (input) : second dimension of A.
     I1, I2 (input) : range of first index to be contoured (inclusive).
     J1, J2 (input) : range of second index to be contoured (inclusive).
     C      (input) : array of NC contour levels; dimension at least NC.
     NC     (input) : +/- number of contour levels (less than or equal
                      to dimension of C). If NC is positive, it is the
                      number of contour levels, and the line-style is
                      chosen automatically as described above. If NC is
                      negative, it is minus the number of contour
                      levels, and the current setting of line-style is
                      used for all the contours.
     PLOT   (input) : the address (name) of a subroutine supplied by
                      the user, which will be called by PGCONX to do
                      the actual plotting. This must be declared
                      EXTERNAL in the program unit calling PGCONX.

    The subroutine PLOT will be called with four arguments:
         CALL PLOT(VISBLE,X,Y,Z)
    where X,Y (input) are real variables corresponding to
    I,J indices of the array A. If  VISBLE (input, integer) is 1,
    PLOT should draw a visible line from the current pen
    position to the world coordinate point corresponding to (X,Y);
    if it is 0, it should move the pen to (X,Y). Z is the value
    of the current contour level, and may be used by PLOT if desired.
    Example:
          SUBROUTINE PLOT (VISBLE,X,Y,Z)
          REAL X, Y, Z, XWORLD, YWORLD
          INTEGER VISBLE
          XWORLD = X*COS(Y) ! this is the user-defined
          YWORLD = X*SIN(Y) ! transformation
          IF (VISBLE.EQ.0) THEN
              CALL PGMOVE (XWORLD, YWORLD)
          ELSE
              CALL PGDRAW (XWORLD, YWORLD)
          END IF
          END

## PGCTAB -- install the color table to be used by PGIMAG

          SUBROUTINE PGCTAB(L, R, G, B, NC, CONTRA, BRIGHT)
          INTEGER NC
          REAL    L(NC), R(NC), G(NC), B(NC), CONTRA, BRIGHT

    Use the given color table to change the color representations of
    all color indexes marked for use by PGIMAG. To change which
    color indexes are thus marked, call PGSCIR before calling PGCTAB
    or PGIMAG. On devices that can change the color representations
    of previously plotted graphics, PGCTAB will also change the colors
    of existing graphics that were plotted with the marked color
    indexes. This feature can then be combined with PGBAND to
    interactively manipulate the displayed colors of data previously
    plotted with PGIMAG.

    Limitations:
     1. Some devices do not propagate color representation changes
        to previously drawn graphics.
     2. Some devices ignore requests to change color representations.
     3. The appearance of specific color representations on grey-scale
        devices is device-dependent.

    Notes:
     To reverse the sense of a color table, change the chosen contrast
     and brightness to -CONTRA and 1-BRIGHT.

     In the following, the term 'color table' refers to the input
     L,R,G,B arrays, whereas 'color ramp' refers to the resulting
     ramp of colors that would be seen with PGWEDG.

    Arguments:
     L      (input)  : An array of NC normalized ramp-intensity levels
                       corresponding to the RGB primary color intensities
                       in R(),G(),B(). Colors on the ramp are linearly
                       interpolated from neighbouring levels.
                       Levels must be sorted in increasing order.
                        0.0 places a color at the beginning of the ramp.
                        1.0 places a color at the end of the ramp.
                       Colors outside these limits are legal, but will
                       not be visible if CONTRA=1.0 and BRIGHT=0.5.
     R      (input)  : An array of NC normalized red intensities.
     G      (input)  : An array of NC normalized green intensities.
     B      (input)  : An array of NC normalized blue intensities.
     NC     (input)  : The number of color table entries.
     CONTRA (input)  : The contrast of the color ramp (normally 1.0).
                       Negative values reverse the direction of the ramp.
     BRIGHT (input)  : The brightness of the color ramp. This is normally
                       0.5, but can sensibly hold any value between 0.0
                       and 1.0. Values at or beyond the latter two
                       extremes, saturate the color ramp with the colors
                       of the respective end of the color table.

## PGCURS -- read cursor position

          INTEGER FUNCTION PGCURS (X, Y, CH)
          REAL X, Y
          CHARACTER*(*) CH

    Read the cursor position and a character typed by the user.
    The position is returned in world coordinates.  PGCURS positions
    the cursor at the position specified, allows the user to move the
    cursor using the joystick or arrow keys or whatever is available on
    the device. When he has positioned the cursor, the user types a
    single character on the keyboard; PGCURS then returns this
    character and the new cursor position (in world coordinates).

    Returns:
     PGCURS         : 1 if the call was successful; 0 if the device
                       has no cursor or some other error occurs.
    Arguments:
     X      (in/out) : the world x-coordinate of the cursor.
     Y      (in/out) : the world y-coordinate of the cursor.
     CH     (output) : the character typed by the user; if the device has
                       no cursor or if some other error occurs, the value
                       CHAR(0) [ASCII NUL character] is returned.

    Note: The cursor coordinates (X,Y) may be changed by PGCURS even if
    the device has no cursor or if the user does not move the cursor.
    Under these circumstances, the position returned in (X,Y) is that of
    the pixel nearest to the requested position.

## PGCURSE -- non-standard alias for PGCURS

          INTEGER FUNCTION PGCURSE (X, Y, CH)
          REAL X, Y
          CHARACTER*1 CH

    See description of PGCURS.

## PGDRAW -- draw a line from the current pen position to a point

          SUBROUTINE PGDRAW (X, Y)
          REAL X, Y

    Draw a line from the current pen position to the point
    with world-coordinates (X,Y). The line is clipped at the edge of the
    current window. The new pen position is (X,Y) in world coordinates.

    Arguments:
     X      (input)  : world x-coordinate of the end point of the line.
     Y      (input)  : world y-coordinate of the end point of the line.

## PGEBUF -- end batch of output (buffer)

          SUBROUTINE PGEBUF

    A call to PGEBUF marks the end of a batch of graphical output begun
    with the last call of PGBBUF.  PGBBUF and PGEBUF calls should always
    be paired. Each call to PGBBUF increments a counter, while each call
    to PGEBUF decrements the counter. When the counter reaches 0, the
    batch of output is written on the output device.

    Arguments: none

## PGEND -- close all open graphics devices

          SUBROUTINE PGEND

    Close and release any open graphics devices. All devices must be
    closed by calling either PGCLOS (for each device) or PGEND before
    the program terminates. If a device is not closed properly, some
    or all of the graphical output may be lost.

    Arguments: none

## PGENV -- set window and viewport and draw labeled frame

          SUBROUTINE PGENV (XMIN, XMAX, YMIN, YMAX, JUST, AXIS)
          REAL XMIN, XMAX, YMIN, YMAX
          INTEGER JUST, AXIS

    Set PGPLOT "Plotter Environment".  PGENV establishes the scaling
    for subsequent calls to PGPT, PGLINE, etc.  The plotter is
    advanced to a new page or panel, clearing the screen if necessary.
    If the "prompt state" is ON (see PGASK), confirmation
    is requested from the user before clearing the screen.
    If requested, a box, axes, labels, etc. are drawn according to
    the setting of argument AXIS.

    Arguments:
     XMIN   (input)  : the world x-coordinate at the bottom left corner
                       of the viewport.
     XMAX   (input)  : the world x-coordinate at the top right corner
                       of the viewport (note XMAX may be less than XMIN).
     YMIN   (input)  : the world y-coordinate at the bottom left corner
                       of the viewport.
     YMAX   (input)  : the world y-coordinate at the top right corner
                       of the viewport (note YMAX may be less than YMIN).
     JUST   (input)  : if JUST=1, the scales of the x and y axes (in
                       world coordinates per inch) will be equal,
                       otherwise they will be scaled independently.
     AXIS   (input)  : controls the plotting of axes, tick marks, etc:
         AXIS = -2 : draw no box, axes or labels;
         AXIS = -1 : draw box only;
         AXIS =  0 : draw box and label it with coordinates;
         AXIS =  1 : same as AXIS=0, but also draw the
                     coordinate axes (X=0, Y=0);
         AXIS =  2 : same as AXIS=1, but also draw grid lines
                     at major increments of the coordinates;
         AXIS = 10 : draw box and label X-axis logarithmically;
         AXIS = 20 : draw box and label Y-axis logarithmically;
         AXIS = 30 : draw box and label both axes logarithmically.

    For other axis options, use routine PGBOX. PGENV can be persuaded to
    call PGBOX with additional axis options by defining an environment
    parameter PGPLOT_ENVOPT containing the required option codes.
    Examples:
      PGPLOT_ENVOPT=P      ! draw Projecting tick marks
      PGPLOT_ENVOPT=I      ! Invert the tick marks
      PGPLOT_ENVOPT=IV     ! Invert tick marks and label y Vertically

## PGERAS -- erase all graphics from current page

          SUBROUTINE PGERAS

    Erase all graphics from the current page (or current panel, if
    the view surface has been divided into panels with PGSUBP).

    Arguments: none

## PGERR1 -- horizontal or vertical error bar

          SUBROUTINE PGERR1 (DIR, X, Y, E, T)
          INTEGER DIR
          REAL X, Y, E
          REAL T

    Plot a single error bar in the direction specified by DIR.
    This routine draws an error bar only; to mark the data point at
    the start of the error bar, an additional call to PGPT is required.
    To plot many error bars, use PGERRB.

    Arguments:
     DIR    (input)  : direction to plot the error bar relative to
                       the data point.
                       One-sided error bar:
                         DIR is 1 for +X (X to X+E);
                                2 for +Y (Y to Y+E);
                                3 for -X (X to X-E);
                                4 for -Y (Y to Y-E).
                       Two-sided error bar:
                         DIR is 5 for +/-X (X-E to X+E);
                                6 for +/-Y (Y-E to Y+E).
     X      (input)  : world x-coordinate of the data.
     Y      (input)  : world y-coordinate of the data.
     E      (input)  : value of error bar distance to be added to the
                       data position in world coordinates.
     T      (input)  : length of terminals to be drawn at the ends
                       of the error bar, as a multiple of the default
                       length; if T = 0.0, no terminals will be drawn.

## PGERRB -- horizontal or vertical error bar

          SUBROUTINE PGERRB (DIR, N, X, Y, E, T)
          INTEGER DIR, N
          REAL X(*), Y(*), E(*)
          REAL T

    Plot error bars in the direction specified by DIR.
    This routine draws an error bar only; to mark the data point at
    the start of the error bar, an additional call to PGPT is required.

    Arguments:
     DIR    (input)  : direction to plot the error bar relative to
                       the data point.
                       One-sided error bar:
                         DIR is 1 for +X (X to X+E);
                                2 for +Y (Y to Y+E);
                                3 for -X (X to X-E);
                                4 for -Y (Y to Y-E).
                       Two-sided error bar:
                         DIR is 5 for +/-X (X-E to X+E);
                                6 for +/-Y (Y-E to Y+E).
     N      (input)  : number of error bars to plot.
     X      (input)  : world x-coordinates of the data.
     Y      (input)  : world y-coordinates of the data.
     E      (input)  : value of error bar distance to be added to the
                       data position in world coordinates.
     T      (input)  : length of terminals to be drawn at the ends
                       of the error bar, as a multiple of the default
                       length; if T = 0.0, no terminals will be drawn.

    Note: the dimension of arrays X, Y, and E must be greater
    than or equal to N. If N is 1, X, Y, and E may be scalar
    variables, or expressions.

## PGERRX -- horizontal error bar

          SUBROUTINE PGERRX (N, X1, X2, Y, T)
          INTEGER N
          REAL X1(*), X2(*), Y(*)
          REAL T

    Plot horizontal error bars.
    This routine draws an error bar only; to mark the data point in
    the middle of the error bar, an additional call to PGPT or
    PGERRY is required.

    Arguments:
     N      (input)  : number of error bars to plot.
     X1     (input)  : world x-coordinates of lower end of the
                       error bars.
     X2     (input)  : world x-coordinates of upper end of the
                       error bars.
     Y      (input)  : world y-coordinates of the data.
     T      (input)  : length of terminals to be drawn at the ends
                       of the error bar, as a multiple of the default
                       length; if T = 0.0, no terminals will be drawn.

    Note: the dimension of arrays X1, X2, and Y must be greater
    than or equal to N. If N is 1, X1, X2, and Y may be scalar
    variables, or expressions, eg:
          CALL PGERRX(1,X-SIGMA,X+SIGMA,Y)

## PGERRY -- vertical error bar

          SUBROUTINE PGERRY (N, X, Y1, Y2, T)
          INTEGER N
          REAL X(*), Y1(*), Y2(*)
          REAL T

    Plot vertical error bars.
    This routine draws an error bar only; to mark the data point in
    the middle of the error bar, an additional call to PGPT or
    PGERRX is required.

    Arguments:
     N      (input)  : number of error bars to plot.
     X      (input)  : world x-coordinates of the data.
     Y1     (input)  : world y-coordinates of top end of the
                       error bars.
     Y2     (input)  : world y-coordinates of bottom end of the
                       error bars.
     T      (input)  : length of terminals to be drawn at the ends
                       of the error bar, as a multiple of the default
                       length; if T = 0.0, no terminals will be drawn.

    Note: the dimension of arrays X, Y1, and Y2 must be greater
    than or equal to N. If N is 1, X, Y1, and Y2 may be scalar
    variables or expressions, eg:
          CALL PGERRY(1,X,Y+SIGMA,Y-SIGMA)

## PGETXT -- erase text from graphics display

          SUBROUTINE PGETXT

    Some graphics terminals display text (the normal interactive dialog)
    on the same screen as graphics. This routine erases the text from the
    view surface without affecting the graphics. It does nothing on
    devices which do not display text on the graphics screen, and on
    devices which do not have this capability.

    Arguments:
     None

## PGFUNT -- function defined by X = F(T), Y = G(T)

          SUBROUTINE PGFUNT (FX, FY, N, TMIN, TMAX, PGFLAG)
          REAL FX, FY
          EXTERNAL FX, FY
          INTEGER N
          REAL TMIN, TMAX
          INTEGER PGFLAG

    Draw a curve defined by parametric equations X = FX(T), Y = FY(T).

    Arguments:
     FX     (external real function): supplied by the user, evaluates
                       X-coordinate.
     FY     (external real function): supplied by the user, evaluates
                       Y-coordinate.
     N      (input)  : the number of points required to define the
                       curve. The functions FX and FY will each be
                       called N+1 times.
     TMIN   (input)  : the minimum value for the parameter T.
     TMAX   (input)  : the maximum value for the parameter T.
     PGFLAG (input)  : if PGFLAG = 1, the curve is plotted in the
                       current window and viewport; if PGFLAG = 0,
                       PGENV is called automatically by PGFUNT to
                       start a new plot with automatic scaling.

    Note: The functions FX and FY must be declared EXTERNAL in the
    Fortran program unit that calls PGFUNT.

## PGFUNX -- function defined by Y = F(X)

          SUBROUTINE PGFUNX (FY, N, XMIN, XMAX, PGFLAG)
          REAL FY
          EXTERNAL FY
          INTEGER N
          REAL XMIN, XMAX
          INTEGER PGFLAG

    Draw a curve defined by the equation Y = FY(X), where FY is a
    user-supplied subroutine.

    Arguments:
     FY     (external real function): supplied by the user, evaluates
                       Y value at a given X-coordinate.
     N      (input)  : the number of points required to define the
                       curve. The function FY will be called N+1 times.
                       If PGFLAG=0 and N is greater than 1000, 1000
                       will be used instead.  If N is less than 1,
                       nothing will be drawn.
     XMIN   (input)  : the minimum value of X.
     XMAX   (input)  : the maximum value of X.
     PGFLAG (input)  : if PGFLAG = 1, the curve is plotted in the
                       current window and viewport; if PGFLAG = 0,
                       PGENV is called automatically by PGFUNX to
                       start a new plot with X limits (XMIN, XMAX)
                       and automatic scaling in Y.

    Note: The function FY must be declared EXTERNAL in the Fortran
    program unit that calls PGFUNX.  It has one argument, the
    x-coordinate at which the y value is required, e.g.
      REAL FUNCTION FY(X)
      REAL X
      FY = .....
      END

## PGFUNY -- function defined by X = F(Y)

          SUBROUTINE PGFUNY (FX, N, YMIN, YMAX, PGFLAG)
          REAL    FX
          EXTERNAL FX
          INTEGER N
          REAL    YMIN, YMAX
          INTEGER PGFLAG

    Draw a curve defined by the equation X = FX(Y), where FY is a
    user-supplied subroutine.

    Arguments:
     FX     (external real function): supplied by the user, evaluates
                       X value at a given Y-coordinate.
     N      (input)  : the number of points required to define the
                       curve. The function FX will be called N+1 times.
                       If PGFLAG=0 and N is greater than 1000, 1000
                       will be used instead.  If N is less than 1,
                       nothing will be drawn.
     YMIN   (input)  : the minimum value of Y.
     YMAX   (input)  : the maximum value of Y.
     PGFLAG (input)  : if PGFLAG = 1, the curve is plotted in the
                       current window and viewport; if PGFLAG = 0,
                       PGENV is called automatically by PGFUNY to
                       start a new plot with Y limits (YMIN, YMAX)
                       and automatic scaling in X.

    Note: The function FX must be declared EXTERNAL in the Fortran
    program unit that calls PGFUNY.  It has one argument, the
    y-coordinate at which the x value is required, e.g.
      REAL FUNCTION FX(Y)
      REAL Y
      FX = .....
      END

## PGGRAY -- gray-scale map of a 2D data array

          SUBROUTINE PGGRAY (A, IDIM, JDIM, I1, I2, J1, J2,
         1                   FG, BG, TR)
          INTEGER IDIM, JDIM, I1, I2, J1, J2
          REAL    A(IDIM,JDIM), FG, BG, TR(6)

    Draw gray-scale map of an array in current window. The subsection
    of the array A defined by indices (I1:I2, J1:J2) is mapped onto
    the view surface world-coordinate system by the transformation
    matrix TR. The resulting quadrilateral region is clipped at the edge
    of the window and shaded with the shade at each point determined
    by the corresponding array value.  The shade is a number in the
    range 0 to 1 obtained by linear interpolation between the background
    level (BG) and the foreground level (FG), i.e.,

      shade = [A(i,j) - BG] / [FG - BG]

    The background level BG can be either less than or greater than the
    foreground level FG.  Points in the array that are outside the range
    BG to FG are assigned shade 0 or 1 as appropriate.

    PGGRAY uses two different algorithms, depending how many color
    indices are available in the color index range specified for images.
    (This range is set with routine PGSCIR, and the current or default
    range can be queried by calling routine PGQCIR).

    If 16 or more color indices are available, PGGRAY first assigns
    color representations to these color indices to give a linear ramp
    between the background color (color index 0) and the foreground color
    (color index 1), and then calls PGIMAG to draw the image using these
    color indices. In this mode, the shaded region is "opaque": every
    pixel is assigned a color.

    If less than 16 color indices are available, PGGRAY uses only
    color index 1, and uses  a "dithering" algorithm to fill in pixels,
    with the shade (computed as above) determining the faction of pixels
    that are filled. In this mode the shaded region is "transparent" and
    allows previously-drawn graphics to show through.

    The transformation matrix TR is used to calculate the world
    coordinates of the center of the "cell" that represents each
    array element. The world coordinates of the center of the cell
    corresponding to array element A(I,J) are given by:

             X = TR(1) + TR(2)*I + TR(3)*J
             Y = TR(4) + TR(5)*I + TR(6)*J

    Usually TR(3) and TR(5) are zero -- unless the coordinate
    transformation involves a rotation or shear.  The corners of the
    quadrilateral region that is shaded by PGGRAY are given by
    applying this transformation to (I1-0.5,J1-0.5), (I2+0.5, J2+0.5).

    Arguments:
     A      (input)  : the array to be plotted.
     IDIM   (input)  : the first dimension of array A.
     JDIM   (input)  : the second dimension of array A.
     I1, I2 (input)  : the inclusive range of the first index
                       (I) to be plotted.
     J1, J2 (input)  : the inclusive range of the second
                       index (J) to be plotted.
     FG     (input)  : the array value which is to appear with the
                       foreground color (corresponding to color index 1).
     BG     (input)  : the array value which is to appear with the
                       background color (corresponding to color index 0).
     TR     (input)  : transformation matrix between array grid and
                       world coordinates.

## PGHI2D -- cross-sections through a 2D data array

          SUBROUTINE PGHI2D (DATA, NXV, NYV, IX1, IX2, IY1, IY2, X, IOFF,
         1                   BIAS, CENTER, YLIMS)
          INTEGER NXV, NYV, IX1, IX2, IY1, IY2
          REAL    DATA(NXV,NYV)
          REAL    X(IX2-IX1+1), YLIMS(IX2-IX1+1)
          INTEGER IOFF
          REAL    BIAS
          LOGICAL CENTER

    Plot a series of cross-sections through a 2D data array.
    Each cross-section is plotted as a hidden line histogram.  The plot
    can be slanted to give a pseudo-3D effect - if this is done, the
    call to PGENV may have to be changed to allow for the increased X
    range that will be needed.

    Arguments:
     DATA   (input)  : the data array to be plotted.
     NXV    (input)  : the first dimension of DATA.
     NYV    (input)  : the second dimension of DATA.
     IX1    (input)
     IX2    (input)
     IY1    (input)
     IY2    (input)  : PGHI2D plots a subset of the input array DATA.
                       This subset is delimited in the first (x)
                       dimension by IX1 and IX2 and the 2nd (y) by IY1
                       and IY2, inclusively. Note: IY2 < IY1 is
                       permitted, resulting in a plot with the
                       cross-sections plotted in reverse Y order.
                       However, IX2 must be => IX1.
     X      (input)  : the abscissae of the bins to be plotted. That is,
                       X(1) should be the X value for DATA(IX1,IY1), and
                       X should have (IX2-IX1+1) elements.  The program
                       has to assume that the X value for DATA(x,y) is
                       the same for all y.
     IOFF   (input)  : an offset in array elements applied to successive
                       cross-sections to produce a slanted effect.  A
                       plot with IOFF > 0 slants to the right, one with
                       IOFF < 0 slants left.
     BIAS   (input)  : a bias value applied to each successive cross-
                       section in order to raise it above the previous
                       cross-section.  This is in the same units as the
                       data.
     CENTER (input)  : if .true., the X values denote the center of the
                       bins; if .false. the X values denote the lower
                       edges (in X) of the bins.
     YLIMS  (input)  : workspace.  Should be an array of at least
                       (IX2-IX1+1) elements.

## PGHIST -- histogram of unbinned data

          SUBROUTINE PGHIST(N, DATA, DATMIN, DATMAX, NBIN, PGFLAG)
          INTEGER N
          REAL    DATA(*)
          REAL    DATMIN, DATMAX
          INTEGER NBIN, PGFLAG

    Draw a histogram of N values of a variable in array
    DATA(1...N) in the range DATMIN to DATMAX using NBIN bins.  Note
    that array elements which fall exactly on the boundary between
    two bins will be counted in the higher bin rather than the
    lower one; and array elements whose value is less than DATMIN or
    greater than or equal to DATMAX will not be counted at all.

    Arguments:
     N      (input)  : the number of data values.
     DATA   (input)  : the data values. Note: the dimension of array
                       DATA must be greater than or equal to N. The
                       first N elements of the array are used.
     DATMIN (input)  : the minimum data value for the histogram.
     DATMAX (input)  : the maximum data value for the histogram.
     NBIN   (input)  : the number of bins to use: the range DATMIN to
                       DATMAX is divided into NBIN equal bins and
                       the number of DATA values in each bin is
                       determined by PGHIST.  NBIN may not exceed 200.
     PGFLAG (input)  : if PGFLAG = 1, the histogram is plotted in the
                       current window and viewport; if PGFLAG = 0,
                       PGENV is called automatically by PGHIST to start
                       a new plot (the x-limits of the window will be
                       DATMIN and DATMAX; the y-limits will be chosen
                       automatically.
                       IF PGFLAG = 2,3 the histogram will be in the same
                       window and viewport but with a filled area style.
                       If pgflag=4,5 as for pgflag = 0,1, but simple
                       line drawn as for PGBIN

## PGIDEN -- write username, date, and time at bottom of plot

          SUBROUTINE PGIDEN

    Write username, date, and time at bottom of plot.

    Arguments: none.

## PGIMAG -- color image from a 2D data array

          SUBROUTINE PGIMAG (A, IDIM, JDIM, I1, I2, J1, J2,
         1                   A1, A2, TR)
          INTEGER IDIM, JDIM, I1, I2, J1, J2
          REAL    A(IDIM,JDIM), A1, A2, TR(6)

    Draw a color image of an array in current window. The subsection
    of the array A defined by indices (I1:I2, J1:J2) is mapped onto
    the view surface world-coordinate system by the transformation
    matrix TR. The resulting quadrilateral region is clipped at the edge
    of the window. Each element of the array is represented in the image
    by a small quadrilateral, which is filled with a color specified by
    the corresponding array value.

    The subroutine uses color indices in the range C1 to C2, which can
    be specified by calling PGSCIR before PGIMAG. The default values
    for C1 and C2 are device-dependent; these values can be determined by
    calling PGQCIR. Note that color representations should be assigned to
    color indices C1 to C2 by calling PGSCR before calling PGIMAG. On some
    devices (but not all), the color representation can be changed after
    the call to PGIMAG by calling PGSCR again.

    Array values in the range A1 to A2 are mapped on to the range of
    color indices C1 to C2, with array values <= A1 being given color
    index C1 and values >= A2 being given color index C2. The mapping
    function for intermediate array values can be specified by
    calling routine PGSITF before PGIMAG; the default is linear.

    On devices which have no available color indices (C1 > C2),
    PGIMAG will return without doing anything. On devices with only
    one color index (C1=C2), all array values map to the same color
    which is rather uninteresting. An image is always "opaque",
    i.e., it obscures all graphical elements previously drawn in
    the region.

    The transformation matrix TR is used to calculate the world
    coordinates of the center of the "cell" that represents each
    array element. The world coordinates of the center of the cell
    corresponding to array element A(I,J) are given by:

             X = TR(1) + TR(2)*I + TR(3)*J
             Y = TR(4) + TR(5)*I + TR(6)*J

    Usually TR(3) and TR(5) are zero -- unless the coordinate
    transformation involves a rotation or shear.  The corners of the
    quadrilateral region that is shaded by PGIMAG are given by
    applying this transformation to (I1-0.5,J1-0.5), (I2+0.5, J2+0.5).

    Arguments:
     A      (input)  : the array to be plotted.
     IDIM   (input)  : the first dimension of array A.
     JDIM   (input)  : the second dimension of array A.
     I1, I2 (input)  : the inclusive range of the first index
                       (I) to be plotted.
     J1, J2 (input)  : the inclusive range of the second
                       index (J) to be plotted.
     A1     (input)  : the array value which is to appear with shade C1.
     A2     (input)  : the array value which is to appear with shade C2.
     TR     (input)  : transformation matrix between array grid and
                       world coordinates.

## PGLAB -- write labels for x-axis, y-axis, and top of plot

          SUBROUTINE PGLAB (XLBL, YLBL, TOPLBL)
          CHARACTER*(*) XLBL, YLBL, TOPLBL

    Write labels outside the viewport. This routine is a simple
    interface to PGMTXT, which should be used if PGLAB is inadequate.

    Arguments:
     XLBL   (input) : a label for the x-axis (centered below the
                      viewport).
     YLBL   (input) : a label for the y-axis (centered to the left
                      of the viewport, drawn vertically).
     TOPLBL (input) : a label for the entire plot (centered above the
                      viewport).

## PGLABEL -- non-standard alias for PGLAB

          SUBROUTINE PGLABEL (XLBL, YLBL, TOPLBL)
          CHARACTER*(*) XLBL, YLBL, TOPLBL

    See description of PGLAB.

## PGLCUR -- draw a line using the cursor

          SUBROUTINE PGLCUR (MAXPT, NPT, X, Y)
          INTEGER MAXPT, NPT
          REAL    X(*), Y(*)

    Interactive routine for user to enter a polyline by use of
    the cursor.  Routine allows user to Add and Delete vertices;
    vertices are joined by straight-line segments.

    Arguments:
     MAXPT  (input)  : maximum number of points that may be accepted.
     NPT    (in/out) : number of points entered; should be zero on
                       first call.
     X      (in/out) : array of x-coordinates (dimension at least MAXPT).
     Y      (in/out) : array of y-coordinates (dimension at least MAXPT).

    Notes:

    (1) On return from the program, cursor points are returned in
    the order they were entered. Routine may be (re-)called with points
    already defined in X,Y (# in NPT), and they will be plotted
    first, before editing.

    (2) User commands: the user types single-character commands
    after positioning the cursor: the following are accepted:
      A (Add)    - add point at current cursor location.
      D (Delete) - delete last-entered point.
      X (eXit)   - leave subroutine.

## PGLDEV -- list available device types on standard output

          SUBROUTINE PGLDEV

    Writes (to standard output) a list of all device types available in
    the current PGPLOT installation.

    Arguments: none.

## PGLEN -- find length of a string in a variety of units

          SUBROUTINE PGLEN (UNITS, STRING, XL, YL)
          REAL XL, YL
          INTEGER UNITS
          CHARACTER*(*) STRING

    Work out length of a string in x and y directions

    Input
     UNITS    :  0 => answer in normalized device coordinates
                 1 => answer in inches
                 2 => answer in mm
                 3 => answer in absolute device coordinates (dots)
                 4 => answer in world coordinates
                 5 => answer as a fraction of the current viewport size

     STRING   :  String of interest
    Output
     XL       :  Length of string in x direction
     YL       :  Length of string in y direction

## PGLINE -- draw a polyline (curve defined by line-segments)

          SUBROUTINE PGLINE (N, XPTS, YPTS)
          INTEGER  N
          REAL     XPTS(*), YPTS(*)

    Primitive routine to draw a Polyline. A polyline is one or more
    connected straight-line segments.  The polyline is drawn using
    the current setting of attributes color-index, line-style, and
    line-width. The polyline is clipped at the edge of the window.

    Arguments:
     N      (input)  : number of points defining the line; the line
                       consists of (N-1) straight-line segments.
                       N should be greater than 1 (if it is 1 or less,
                       nothing will be drawn).
     XPTS   (input)  : world x-coordinates of the points.
     YPTS   (input)  : world y-coordinates of the points.

    The dimension of arrays X and Y must be greater than or equal to N.
    The "pen position" is changed to (X(N),Y(N)) in world coordinates
    (if N > 1).

## PGMOVE -- move pen (change current pen position)

          SUBROUTINE PGMOVE (X, Y)
          REAL X, Y

    Primitive routine to move the "pen" to the point with world
    coordinates (X,Y). No line is drawn.

    Arguments:
     X      (input)  : world x-coordinate of the new pen position.
     Y      (input)  : world y-coordinate of the new pen position.

## PGMTEXT -- non-standard alias for PGMTXT

          SUBROUTINE PGMTEXT (SIDE, DISP, COORD, FJUST, TEXT)
          CHARACTER*(*) SIDE, TEXT
          REAL DISP, COORD, FJUST

    See description of PGMTXT.

## PGMTXT -- write text at position relative to viewport

          SUBROUTINE PGMTXT (SIDE, DISP, COORD, FJUST, TEXT)
          CHARACTER*(*) SIDE, TEXT
          REAL DISP, COORD, FJUST

    Write text at a position specified relative to the viewport (outside
    or inside).  This routine is useful for annotating graphs. It is used
    by routine PGLAB.  The text is written using the current values of
    attributes color-index, line-width, character-height, and
    character-font.

    Arguments:
     SIDE   (input)  : must include one of the characters 'B', 'L', 'T',
                       or 'R' signifying the Bottom, Left, Top, or Right
                       margin of the viewport. If it includes 'LV' or
                       'RV', the string is written perpendicular to the
                       frame rather than parallel to it.
     DISP   (input)  : the displacement of the character string from the
                       specified edge of the viewport, measured outwards
                       from the viewport in units of the character
                       height. Use a negative value to write inside the
                       viewport, a positive value to write outside.
     COORD  (input)  : the location of the character string along the
                       specified edge of the viewport, as a fraction of
                       the length of the edge.
     FJUST  (input)  : controls justification of the string parallel to
                       the specified edge of the viewport. If
                       FJUST = 0.0, the left-hand end of the string will
                       be placed at COORD; if JUST = 0.5, the center of
                       the string will be placed at COORD; if JUST = 1.0,
                       the right-hand end of the string will be placed at
                       at COORD. Other values between 0 and 1 give inter-
                       mediate placing, but they are not very useful.
     TEXT   (input) :  the text string to be plotted. Trailing spaces are
                       ignored when justifying the string, but leading
                       spaces are significant.

## PGNCUR -- mark a set of points using the cursor

          SUBROUTINE PGNCUR (MAXPT, NPT, X, Y, SYMBOL)
          INTEGER MAXPT, NPT
          REAL    X(*), Y(*)
          INTEGER SYMBOL

    Interactive routine for user to enter data points by use of
    the cursor.  Routine allows user to Add and Delete points.  The
    points are returned in order of increasing x-coordinate, not in the
    order they were entered.

    Arguments:
     MAXPT  (input)  : maximum number of points that may be accepted.
     NPT    (in/out) : number of points entered; should be zero on
                       first call.
     X      (in/out) : array of x-coordinates.
     Y      (in/out) : array of y-coordinates.
     SYMBOL (input)  : code number of symbol to use for marking
                       entered points (see PGPT).

    Note (1): The dimension of arrays X and Y must be greater than or
    equal to MAXPT.

    Note (2): On return from the program, cursor points are returned in
    increasing order of X. Routine may be (re-)called with points
    already defined in X,Y (number in NPT), and they will be plotted
    first, before editing.

    Note (3): User commands: the user types single-character commands
    after positioning the cursor: the following are accepted:
    A (Add)    - add point at current cursor location.
    D (Delete) - delete nearest point to cursor.
    X (eXit)   - leave subroutine.

## PGNCURSE -- non-standard alias for PGNCUR

          SUBROUTINE PGNCURSE (MAXPT, NPT, X, Y, SYMBOL)
          INTEGER MAXPT, NPT
          REAL    X(*), Y(*)
          INTEGER SYMBOL

    See description of PGNCUR.

## PGNUMB -- convert a number into a plottable character string

          SUBROUTINE PGNUMB (MM, PP, FORM, STRING, NC)
          INTEGER MM, PP, FORM
          CHARACTER*(*) STRING
          INTEGER NC

    This routine converts a number into a decimal character
    representation. To avoid problems of floating-point roundoff, the
    number must be provided as an integer (MM) multiplied by a power of 10
    (10**PP).  The output string retains only significant digits of MM,
    and will be in either integer format (123), decimal format (0.0123),
    or exponential format (1.23x10**5). Standard escape sequences \u, \d
    raise the exponent and \x is used for the multiplication sign.
    This routine is used by PGBOX to create numeric labels for a plot.

    Formatting rules:
      (a) Decimal notation (FORM=1):
          - Trailing zeros to the right of the decimal sign are
            omitted
          - The decimal sign is omitted if there are no digits
            to the right of it
          - When the decimal sign is placed before the first digit
            of the number, a zero is placed before the decimal sign
          - The decimal sign is a period (.)
          - No spaces are placed between digits (ie digits are not
            grouped in threes as they should be)
          - A leading minus (-) is added if the number is negative
      (b) Exponential notation (FORM=2):
          - The exponent is adjusted to put just one (non-zero)
            digit before the decimal sign
          - The mantissa is formatted as in (a), unless its value is
            1 in which case it and the multiplication sign are omitted
          - If the power of 10 is not zero and the mantissa is not
            zero, an exponent of the form \x10\u[-]nnn is appended,
            where \x is a multiplication sign (cross), \u is an escape
            sequence to raise the exponent, and as many digits nnn
            are used as needed
      (c) Automatic choice (FORM=0):
            Decimal notation is used if the absolute value of the
            number is less than 10000 or greater than or equal to
            0.01. Otherwise exponential notation is used.

    Arguments:
     MM     (input)
     PP     (input)  : the value to be formatted is MM*10**PP.
     FORM   (input)  : controls how the number is formatted:
                       FORM = 0 -- use either decimal or exponential
                       FORM = 1 -- use decimal notation
                       FORM = 2 -- use exponential notation
     STRING (output) : the formatted character string, left justified.
                       If the length of STRING is insufficient, a single
                       asterisk is returned, and NC=1.
     NC     (output) : the number of characters used in STRING:
                       the string to be printed is STRING(1:NC).

## PGOLIN -- mark a set of points using the cursor

          SUBROUTINE PGOLIN (MAXPT, NPT, X, Y, SYMBOL)
          INTEGER MAXPT, NPT
          REAL    X(*), Y(*)
          INTEGER SYMBOL

    Interactive routine for user to enter data points by use of
    the cursor.  Routine allows user to Add and Delete points.  The
    points are returned in the order that they were entered (unlike
    PGNCUR).

    Arguments:
     MAXPT  (input)  : maximum number of points that may be accepted.
     NPT    (in/out) : number of points entered; should be zero on
                       first call.
     X      (in/out) : array of x-coordinates.
     Y      (in/out) : array of y-coordinates.
     SYMBOL (input)  : code number of symbol to use for marking
                       entered points (see PGPT).

    Note (1): The dimension of arrays X and Y must be greater than or
    equal to MAXPT.

    Note (2): On return from the program, cursor points are returned in
    the order they were entered. Routine may be (re-)called with points
    already defined in X,Y (number in NPT), and they will be plotted
    first, before editing.

    Note (3): User commands: the user types single-character commands
    after positioning the cursor: the following are accepted:
    A (Add)    - add point at current cursor location.
    D (Delete) - delete the last point entered.
    X (eXit)   - leave subroutine.

## PGOPEN -- open a graphics device

          INTEGER FUNCTION PGOPEN (DEVICE)
          CHARACTER*(*) DEVICE

    Open a graphics device for PGPLOT output. If the device is
    opened successfully, it becomes the selected device to which
    graphics output is directed until another device is selected
    with PGSLCT or the device is closed with PGCLOS.

    The value returned by PGOPEN should be tested to ensure that
    the device was opened successfully, e.g.,

          ISTAT = PGOPEN('plot.ps/PS')
          IF (ISTAT .LE. 0 ) STOP

    Note that PGOPEN must be declared INTEGER in the calling program.

    The DEVICE argument is a character constant or variable; its value
    should be one of the following:

    (1) A complete device specification of the form 'device/type' or
        'file/type', where 'type' is one of the allowed PGPLOT device
        types (installation-dependent) and 'device' or 'file' is the
        name of a graphics device or disk file appropriate for this type.
        The 'device' or 'file' may contain '/' characters; the final
        '/' delimits the 'type'. If necessary to avoid ambiguity,
        the 'device' part of the string may be enclosed in double
        quotation marks.
    (2) A device specification of the form '/type', where 'type' is one
        of the allowed PGPLOT device types. PGPLOT supplies a default
        file or device name appropriate for this device type.
    (3) A device specification with '/type' omitted; in this case
        the type is taken from the environment variable PGPLOT_TYPE,
        if defined (e.g., setenv PGPLOT_TYPE PS). Because of possible
        confusion with '/' in file-names, omitting the device type
        in this way is not recommended.
    (4) A blank string (' '); in this case, PGOPEN will use the value
        of environment variable PGPLOT_DEV as the device specification,
        or '/NULL' if the environment variable is undefined.
    (5) A single question mark, with optional trailing spaces ('?'); in
        this case, PGPLOT will prompt the user to supply the device
        specification, with a prompt string of the form
            'Graphics device/type (? to see list, default XXX):'
        where 'XXX' is the default (value of environment variable
        PGPLOT_DEV).
    (6) A non-blank string in which the first character is a question
        mark (e.g., '?Device: '); in this case, PGPLOT will prompt the
        user to supply the device specification, using the supplied
        string as the prompt (without the leading question mark but
        including any trailing spaces).

    In cases (5) and (6), the device specification is read from the
    standard input. The user should respond to the prompt with a device
    specification of the form (1), (2), or (3). If the user types a
    question-mark in response to the prompt, a list of available device
    types is displayed and the prompt is re-issued. If the user supplies
    an invalid device specification, the prompt is re-issued. If the user
    responds with an end-of-file character, e.g., ctrl-D in UNIX, program
    execution is aborted; this  avoids the possibility of an infinite
    prompting loop.  A programmer should avoid use of PGPLOT-prompting
    if this behavior is not desirable.

    The device type is case-insensitive (e.g., '/ps' and '/PS' are
    equivalent). The device or file name may be case-sensitive in some
    operating systems.

    Examples of valid DEVICE arguments:

    (1)  'plot.ps/ps', 'dir/plot.ps/ps', '"dir/plot.ps"/ps',
         'user:[tjp.plots]plot.ps/PS'
    (2)  '/ps'      (PGPLOT interprets this as 'pgplot.ps/ps')
    (3)  'plot.ps'  (if PGPLOT_TYPE is defined as 'ps', PGPLOT
                     interprets this as 'plot.ps/ps')
    (4)  '   '      (if PGPLOT_DEV is defined)
    (5)  '?  '
    (6)  '?Device specification for PGPLOT: '

    [This routine was added to PGPLOT in Version 5.1.0. Older programs
    use PGBEG instead.]

    Returns:
     PGOPEN          : returns either a positive value, the
                       identifier of the graphics device for use with
                       PGSLCT, or a 0 or negative value indicating an
                       error. In the event of error a message is
                       written on the standard error unit.
    Arguments:
     DEVICE  (input) : the 'device specification' for the plot device
                       (see above).

## PGPAGE -- advance to new page

          SUBROUTINE PGPAGE

    Advance plotter to a new page or panel, clearing the screen if
    necessary. If the "prompt state" is ON (see PGASK), confirmation is
    requested from the user before clearing the screen. If the view
    surface has been subdivided into panels with PGBEG or PGSUBP, then
    PGPAGE advances to the next panel, and if the current panel is the
    last on the page, PGPAGE clears the screen or starts a new sheet of
    paper.  PGPAGE does not change the PGPLOT window or the viewport
    (in normalized device coordinates); but note that if the size of the
    view-surface is changed externally (e.g., by a workstation window
    manager) the size of the viewport is changed in proportion.

    Arguments: none

## PGPANL -- switch to a different panel on the view surface

          SUBROUTINE PGPANL(IX, IY)
          INTEGER IX, IY

    Start plotting in a different panel. If the view surface has been
    divided into panels by PGBEG or PGSUBP, this routine can be used to
    move to a different panel. Note that PGPLOT does not remember what
    viewport and window were in use in each panel; these should be reset
    if necessary after calling PGPANL. Nor does PGPLOT clear the panel:
    call PGERAS after calling PGPANL to do this.

    Arguments:
     IX     (input)  : the horizontal index of the panel (in the range
                       1 <= IX <= number of panels in horizontal
                       direction).
     IY     (input)  : the vertical index of the panel (in the range
                       1 <= IY <= number of panels in horizontal
                       direction).

## PGPAP -- change the size of the view surface

          SUBROUTINE PGPAP (WIDTH, ASPECT)
          REAL WIDTH, ASPECT

    This routine changes the size of the view surface ("paper size") to a
    specified width and aspect ratio (height/width), in so far as this is
    possible on the specific device. It is always possible to obtain a
    view surface smaller than the default size; on some devices (e.g.,
    printers that print on roll or fan-feed paper) it is possible to
    obtain a view surface larger than the default.

    This routine should be called either immediately after PGBEG or
    immediately before PGPAGE. The new size applies to all subsequent
    images until the next call to PGPAP.

    Arguments:
     WIDTH  (input)  : the requested width of the view surface in inches;
                       if WIDTH=0.0, PGPAP will obtain the largest view
                       surface available consistent with argument ASPECT.
                       (1 inch = 25.4 mm.)
     ASPECT (input)  : the aspect ratio (height/width) of the view
                       surface; e.g., ASPECT=1.0 gives a square view
                       surface, ASPECT=0.618 gives a horizontal
                       rectangle, ASPECT=1.618 gives a vertical rectangle.

## PGPAPER -- non-standard alias for PGPAP

          SUBROUTINE PGPAPER (WIDTH, ASPECT)
          REAL WIDTH, ASPECT

    See description of PGPAP.

## PGPIXL -- draw pixels

          SUBROUTINE PGPIXL (IA, IDIM, JDIM, I1, I2, J1, J2,
         1                   X1, X2, Y1, Y2)
          INTEGER IDIM, JDIM, I1, I2, J1, J2
          INTEGER IA(IDIM,JDIM)
          REAL    X1, X2, Y1, Y2

    Draw lots of solid-filled (tiny) rectangles aligned with the
    coordinate axes. Best performance is achieved when output is
    directed to a pixel-oriented device and the rectangles coincide
    with the pixels on the device. In other cases, pixel output is
    emulated.

    The subsection of the array IA defined by indices (I1:I2, J1:J2)
    is mapped onto world-coordinate rectangle defined by X1, X2, Y1
    and Y2. This rectangle is divided into (I2 - I1 + 1) * (J2 - J1 + 1)
    small rectangles. Each of these small rectangles is solid-filled
    with the color index specified by the corresponding element of
    IA.

    On most devices, the output region is "opaque", i.e., it obscures
    all graphical elements previously drawn in the region. But on
    devices that do not have erase capability, the background shade
    is "transparent" and allows previously-drawn graphics to show
    through.

    Arguments:
     IA     (input)  : the array to be plotted.
     IDIM   (input)  : the first dimension of array A.
     JDIM   (input)  : the second dimension of array A.
     I1, I2 (input)  : the inclusive range of the first index
                       (I) to be plotted.
     J1, J2 (input)  : the inclusive range of the second
                       index (J) to be plotted.
     X1, Y1 (input)  : world coordinates of one corner of the output
                       region
     X2, Y2 (input)  : world coordinates of the opposite corner of the
                       output region

## PGPNTS -- draw several graph markers, not all the same

          SUBROUTINE PGPNTS (N, X, Y, SYMBOL, NS)
          INTEGER N, NS
          REAL X(*), Y(*)
          INTEGER SYMBOL(*)

    Draw Graph Markers. Unlike PGPT, this routine can draw a different
    symbol at each point. The markers are drawn using the current values
    of attributes color-index, line-width, and character-height
    (character-font applies if the symbol number is >31).  If the point
    to be marked lies outside the window, no marker is drawn.  The "pen
    position" is changed to (XPTS(N),YPTS(N)) in world coordinates
    (if N > 0).

    Arguments:
     N      (input)  : number of points to mark.
     X      (input)  : world x-coordinate of the points.
     Y      (input)  : world y-coordinate of the points.
     SYMBOL (input)  : code number of the symbol to be plotted at each
                       point (see PGPT).
     NS     (input)  : number of values in the SYMBOL array.  If NS <= N,
                       then the first NS points are drawn using the value
                       of SYMBOL(I) at (X(I), Y(I)) and SYMBOL(1) for all
                       the values of (X(I), Y(I)) where I > NS.

    Note: the dimension of arrays X and Y must be greater than or equal
    to N and the dimension of the array SYMBOL must be greater than or
    equal to NS.  If N is 1, X and Y may be scalars (constants or
    variables).  If NS is 1, then SYMBOL may be a scalar.  If N is
    less than 1, nothing is drawn.

## PGPOINT -- non-standard alias for PGPT

          SUBROUTINE PGPOINT (N, XPTS, YPTS, SYMBOL)
          INTEGER N
          REAL XPTS(*), YPTS(*)
          INTEGER SYMBOL

    See description of PGPT.

## PGPOLY -- draw a polygon, using fill-area attributes

          SUBROUTINE PGPOLY (N, XPTS, YPTS)
          INTEGER N
          REAL XPTS(*), YPTS(*)

    Fill-area primitive routine: shade the interior of a closed
    polygon in the current window.  The action of this routine depends
    on the setting of the Fill-Area Style attribute (see PGSFS).
    The polygon is clipped at the edge of the
    window. The pen position is changed to (XPTS(1),YPTS(1)) in world
    coordinates (if N > 1).  If the polygon is not convex, a point is
    assumed to lie inside the polygon if a straight line drawn to
    infinity intersects and odd number of the polygon's edges.

    Arguments:
     N      (input)  : number of points defining the polygon; the
                       line consists of N straight-line segments,
                       joining points 1 to 2, 2 to 3,... N-1 to N, N to 1.
                       N should be greater than 2 (if it is 2 or less,
                       nothing will be drawn).
     XPTS   (input)  : world x-coordinates of the vertices.
     YPTS   (input)  : world y-coordinates of the vertices.
                       Note: the dimension of arrays XPTS and YPTS must be
                       greater than or equal to N.

## PGPT -- draw several graph markers

          SUBROUTINE PGPT (N, XPTS, YPTS, SYMBOL)
          INTEGER N
          REAL XPTS(*), YPTS(*)
          INTEGER SYMBOL

    Primitive routine to draw Graph Markers (polymarker). The markers
    are drawn using the current values of attributes color-index,
    line-width, and character-height (character-font applies if the symbol
    number is >31).  If the point to be marked lies outside the window,
    no marker is drawn.  The "pen position" is changed to
    (XPTS(N),YPTS(N)) in world coordinates (if N > 0).

    Arguments:
     N      (input)  : number of points to mark.
     XPTS   (input)  : world x-coordinates of the points.
     YPTS   (input)  : world y-coordinates of the points.
     SYMBOL (input)  : code number of the symbol to be drawn at each
                       point:
                       -1, -2  : a single dot (diameter = current
                                 line width).
                       -3..-31 : a regular polygon with ABS(SYMBOL)
                                 edges (style set by current fill style).
                       0..31   : standard marker symbols.
                       32..127 : ASCII characters (in current font).
                                 e.g. to use letter F as a marker, let
                                 SYMBOL = ICHAR('F').
                       > 127  :  a Hershey symbol number.

    Note: the dimension of arrays X and Y must be greater than or equal
    to N. If N is 1, X and Y may be scalars (constants or variables). If
    N is less than 1, nothing is drawn.

## PGPT1 -- draw one graph marker

          SUBROUTINE PGPT1 (XPT, YPT, SYMBOL)
          REAL XPT, YPT
          INTEGER SYMBOL

    Primitive routine to draw a single Graph Marker at a specified point.
    The marker is drawn using the current values of attributes
    color-index, line-width, and character-height (character-font applies
    if the symbol number is >31).  If the point to be marked lies outside
    the window, no marker is drawn.  The "pen position" is changed to
    (XPT,YPT) in world coordinates.

    To draw several markers with coordinates specified by X and Y
    arrays, use routine PGPT.

    Arguments:
     XPT    (input)  : world x-coordinate of the point.
     YPT    (input)  : world y-coordinate of the point.
     SYMBOL (input)  : code number of the symbol to be drawn:
                       -1, -2  : a single dot (diameter = current
                                 line width).
                       -3..-31 : a regular polygon with ABS(SYMBOL)
                                 edges (style set by current fill style).
                       0..31   : standard marker symbols.
                       32..127 : ASCII characters (in current font).
                                 e.g. to use letter F as a marker, let
                                 SYMBOL = ICHAR('F').
                       > 127  :  a Hershey symbol number.

## PGPTEXT -- non-standard alias for PGPTXT

          SUBROUTINE PGPTEXT (X, Y, ANGLE, FJUST, TEXT)
          REAL X, Y, ANGLE, FJUST
          CHARACTER*(*) TEXT

    See description of PGPTXT.

## PGPTXT -- write text at arbitrary position and angle

          SUBROUTINE PGPTXT (X, Y, ANGLE, FJUST, TEXT)
          REAL X, Y, ANGLE, FJUST
          CHARACTER*(*) TEXT

    Primitive routine for drawing text. The text may be drawn at any
    angle with the horizontal, and may be centered or left- or right-
    justified at a specified position.  Routine PGTEXT provides a
    simple interface to PGPTXT for horizontal strings. Text is drawn
    using the current values of attributes color-index, line-width,
    character-height, and character-font.  Text is NOT subject to
    clipping at the edge of the window.

    Arguments:
     X      (input)  : world x-coordinate.
     Y      (input)  : world y-coordinate. The string is drawn with the
                       baseline of all the characters passing through
                       point (X,Y); the positioning of the string along
                       this line is controlled by argument FJUST.
     ANGLE  (input)  : angle, in degrees, that the baseline is to make
                       with the horizontal, increasing counter-clockwise
                       (0.0 is horizontal).
     FJUST  (input)  : controls horizontal justification of the string.
                       If FJUST = 0.0, the string will be left-justified
                       at the point (X,Y); if FJUST = 0.5, it will be
                       centered, and if FJUST = 1.0, it will be right
                       justified. [Other values of FJUST give other
                       justifications.]
     TEXT   (input)  : the character string to be plotted.

## PGQAH -- inquire arrow-head style

          SUBROUTINE PGQAH (FS, ANGLE, BARB)
          INTEGER  FS
          REAL ANGLE, BARB

    Query the style to be used for arrowheads drawn with routine PGARRO.

    Argument:
     FS     (output) : FS = 1 => filled; FS = 2 => outline.
     ANGLE  (output) : the acute angle of the arrow point, in degrees.
     BARB   (output) : the fraction of the triangular arrow-head that
                       is cut away from the back.

## PGQCF -- inquire character font

          SUBROUTINE PGQCF (FONT)
          INTEGER  FONT

    Query the current Character Font (set by routine PGSCF).

    Argument:
     FONT   (output)   : the current font number (in range 1-4).

## PGQCH -- inquire character height

          SUBROUTINE PGQCH (SIZE)
          REAL SIZE

    Query the Character Size attribute (set by routine PGSCH).

    Argument:
     SIZE   (output) : current character size (dimensionless multiple of
                       the default size).

## PGQCI -- inquire color index

          SUBROUTINE PGQCI (CI)
          INTEGER  CI

    Query the Color Index attribute (set by routine PGSCI).

    Argument:
     CI     (output) : the current color index (in range 0-max). This is
                       the color index actually in use, and may differ
                       from the color index last requested by PGSCI if
                       that index is not available on the output device.

## PGQCIR -- inquire color index range

          SUBROUTINE PGQCIR(ICILO, ICIHI)
          INTEGER   ICILO, ICIHI

    Query the color index range to be used for producing images with
    PGGRAY or PGIMAG, as set by routine PGSCIR or by device default.

    Arguments:
     ICILO  (output) : the lowest color index to use for images
     ICIHI  (output) : the highest color index to use for images

## PGQCLP -- inquire clipping status

          SUBROUTINE PGQCLP(STATE)
          INTEGER  STATE

    Query the current clipping status (set by routine PGSCLP).

    Argument:
     STATE  (output) : receives the clipping status (0 => disabled,
                       1 => enabled).

## PGQCOL -- inquire color capability

          SUBROUTINE PGQCOL (CI1, CI2)
          INTEGER  CI1, CI2

    Query the range of color indices available on the current device.

    Argument:
     CI1    (output) : the minimum available color index. This will be
                       either 0 if the device can write in the
                       background color, or 1 if not.
     CI2    (output) : the maximum available color index. This will be
                       1 if the device has no color capability, or a
                       larger number (e.g., 3, 7, 15, 255).

## PGQCR -- inquire color representation

          SUBROUTINE PGQCR (CI, CR, CG, CB)
          INTEGER CI
          REAL    CR, CG, CB

    Query the RGB colors associated with a color index.

    Arguments:
     CI  (input)  : color index
     CR  (output) : red, green and blue intensities
     CG  (output)   in the range 0.0 to 1.0
     CB  (output)

## PGQCS -- inquire character height in a variety of units

          SUBROUTINE PGQCS(UNITS, XCH, YCH)
          INTEGER UNITS
          REAL XCH, YCH

    Return the current PGPLOT character height in a variety of units.
    This routine provides facilities that are not available via PGQCH.
    Use PGQCS if the character height is required in units other than
    those used in PGSCH.

    The PGPLOT "character height" is a dimension that scales with the
    size of the view surface and with the scale-factor specified with
    routine PGSCH. The default value is 1/40th of the height or width
    of the view surface (whichever is less); this value is then
    multiplied by the scale-factor supplied with PGSCH. Note that it
    is a nominal height only; the actual character size depends on the
    font and is usually somewhat smaller.

    Arguments:
     UNITS  (input)  : Used to specify the units of the output value:
                       UNITS = 0 : normalized device coordinates
                       UNITS = 1 : inches
                       UNITS = 2 : millimeters
                       UNITS = 3 : pixels
                       UNITS = 4 : world coordinates
                       Other values give an error message, and are
                       treated as 0.
     XCH    (output) : The character height for text written with a
                       vertical baseline.
     YCH    (output) : The character height for text written with
                       a horizontal baseline (the usual case).

    The character height is returned in both XCH and YCH.

    If UNITS=1 or UNITS=2, XCH and YCH both receive the same value.

    If UNITS=3, XCH receives the height in horizontal pixel units, and YCH
    receives the height in vertical pixel units; on devices for which the
    pixels are not square, XCH and YCH will be different.

    If UNITS=4, XCH receives the height in horizontal world coordinates
    (as used for the x-axis), and YCH receives the height in vertical
    world coordinates (as used for the y-axis). Unless special care has
    been taken to achive equal world-coordinate scales on both axes, the
    values of XCH and YCH will be different.

    If UNITS=0, XCH receives the character height as a fraction of the
    horizontal dimension of the view surface, and YCH receives the
    character height as a fraction of the vertical dimension of the view
    surface.

## PGQDT -- inquire name of nth available device type

          SUBROUTINE PGQDT(N, TYPE, TLEN, DESCR, DLEN, INTER)
          INTEGER N
          CHARACTER*(*) TYPE, DESCR
          INTEGER TLEN, DLEN, INTER

    Return the name of the Nth available device type as a character
    string. The number of available types can be determined by calling
    PGQNDT. If the value of N supplied is outside the range from 1 to
    the number of available types, the routine returns DLEN=TLEN=0.

    Arguments:
     N      (input)  : the number of the device type (1..maximum).
     TYPE   (output) : receives the character device-type code of the
                       Nth device type. The argument supplied should be
                       large enough for at least 8 characters. The first
                       character in the string is a '/' character.
     TLEN   (output) : receives the number of characters in TYPE,
                       excluding trailing blanks.
     DESCR  (output) : receives a description of the device type. The
                       argument supplied should be large enough for at
                       least 64 characters.
     DLEN   (output) : receives the number of characters in DESCR,
                       excluding trailing blanks.
     INTER  (output) : receives 1 if the device type is an interactive
                       one, 0 otherwise.

## PGQFS -- inquire fill-area style

          SUBROUTINE PGQFS (FS)
          INTEGER  FS

    Query the current Fill-Area Style attribute (set by routine
    PGSFS).

    Argument:
     FS     (output) : the current fill-area style:
                         FS = 1 => solid (default)
                         FS = 2 => outline
                         FS = 3 => hatched
                         FS = 4 => cross-hatched

## PGQHS -- inquire hatching style

          SUBROUTINE PGQHS (ANGLE, SEPN, PHASE)
          REAL ANGLE, SEPN, PHASE

    Query the style to be used hatching (fill area with fill-style 3).

    Arguments:
     ANGLE  (output) : the angle the hatch lines make with the
                       horizontal, in degrees, increasing
                       counterclockwise (this is an angle on the
                       view surface, not in world-coordinate space).
     SEPN   (output) : the spacing of the hatch lines. The unit spacing
                       is 1 percent of the smaller of the height or
                       width of the view surface.
     PHASE  (output) : a real number between 0 and 1; the hatch lines
                       are displaced by this fraction of SEPN from a
                       fixed reference.  Adjacent regions hatched with the
                       same PHASE have contiguous hatch lines.

## PGQID -- inquire current device identifier

          SUBROUTINE PGQID (ID)
          INTEGER  ID

    This subroutine returns the identifier of the currently
    selected device, or 0 if no device is selected.  The identifier is
    assigned when PGOPEN is called to open the device, and may be used
    as an argument to PGSLCT.  Each open device has a different
    identifier.

    [This routine was added to PGPLOT in Version 5.1.0.]

    Argument:
     ID     (output) : the identifier of the current device, or 0 if
                       no device is currently selected.

## PGQINF -- inquire PGPLOT general information

          SUBROUTINE PGQINF (ITEM, VALUE, LENGTH)
          CHARACTER*(*) ITEM, VALUE
          INTEGER LENGTH

    This routine can be used to obtain miscellaneous information about
    the PGPLOT environment. Input is a character string defining the
    information required, and output is a character string containing the
    requested information.

    The following item codes are accepted (note that the strings must
    match exactly, except for case, but only the first 8 characters are
    significant). For items marked *, PGPLOT must be in the OPEN state
    for the inquiry to succeed. If the inquiry is unsuccessful, either
    because the item code is not recognized or because the information
    is not available, a question mark ('?') is returned.

      'VERSION'     - version of PGPLOT software in use.
      'STATE'       - status of PGPLOT ('OPEN' if a graphics device
                      is open for output, 'CLOSED' otherwise).
      'USER'        - the username associated with the calling program.
      'NOW'         - current date and time (e.g., '17-FEB-1986 10:04').
      'DEVICE'    * - current PGPLOT device or file.
      'FILE'      * - current PGPLOT device or file.
      'TYPE'      * - device-type of the current PGPLOT device.
      'DEV/TYPE'  * - current PGPLOT device and type, in a form which
                      is acceptable as an argument for PGBEG.
      'HARDCOPY'  * - is the current device a hardcopy device? ('YES' or
                      'NO').
      'TERMINAL'  * - is the current device the user's interactive
                      terminal? ('YES' or 'NO').
      'CURSOR'    * - does the current device have a graphics cursor?
                      ('YES' or 'NO').
      'SCROLL'    * - does current device have rectangle-scroll
                      capability ('YES' or 'NO'); see PGSCRL.

    Arguments:
     ITEM  (input)  : character string defining the information to
                      be returned; see above for a list of possible
                      values.
     VALUE (output) : returns a character-string containing the
                      requested information, truncated to the length
                      of the supplied string or padded on the right with
                      spaces if necessary.
     LENGTH (output): the number of characters returned in VALUE
                      (excluding trailing blanks).

## PGQITF -- inquire image transfer function

          SUBROUTINE PGQITF (ITF)
          INTEGER  ITF

    Return the Image Transfer Function as set by default or by a previous
    call to PGSITF. The Image Transfer Function is used by routines
    PGIMAG, PGGRAY, and PGWEDG.

    Argument:
     ITF    (output) : type of transfer function (see PGSITF)

## PGQLS -- inquire line style

          SUBROUTINE PGQLS (LS)
          INTEGER  LS

    Query the current Line Style attribute (set by routine PGSLS).

    Argument:
     LS     (output) : the current line-style attribute (in range 1-5).

## PGQLW -- inquire line width

          SUBROUTINE PGQLW (LW)
          INTEGER  LW

    Query the current Line-Width attribute (set by routine PGSLW).

    Argument:
     LW     (output)  : the line-width (in range 1-201).

## PGQNDT -- inquire number of available device types

          SUBROUTINE PGQNDT(N)
          INTEGER N

    Return the number of available device types. This routine is
    usually used in conjunction with PGQDT to get a list of the
    available device types.

    Arguments:
     N      (output) : the number of available device types.

## PGQPOS -- inquire current pen position

          SUBROUTINE PGQPOS (X, Y)
          REAL X, Y

    Query the current "pen" position in world C coordinates (X,Y).

    Arguments:
     X      (output)  : world x-coordinate of the pen position.
     Y      (output)  : world y-coordinate of the pen position.

## PGQTBG -- inquire text background color index

          SUBROUTINE PGQTBG (TBCI)
          INTEGER  TBCI

    Query the current Text Background Color Index (set by routine
    PGSTBG).

    Argument:
     TBCI   (output) : receives the current text background color index.

## PGQTXT -- find bounding box of text string

          SUBROUTINE PGQTXT (X, Y, ANGLE, FJUST, TEXT, XBOX, YBOX)
          REAL X, Y, ANGLE, FJUST
          CHARACTER*(*) TEXT
          REAL XBOX(4), YBOX(4)

    This routine returns a bounding box for a text string. Instead
    of drawing the string as routine PGPTXT does, it returns in XBOX
    and YBOX the coordinates of the corners of a rectangle parallel
    to the string baseline that just encloses the string. The four
    corners are in the order: lower left, upper left, upper right,
    lower right (where left and right refer to the first and last
    characters in the string).

    If the string is blank or contains no drawable characters, all
    four elements of XBOX and YBOX are assigned the starting point
    of the string, (X,Y).

    Arguments:
     X, Y, ANGLE, FJUST, TEXT (input) : these arguments are the same as
                       the corrresponding arguments in PGPTXT.
     XBOX, YBOX (output) : arrays of dimension 4; on output, they
                       contain the world coordinates of the bounding
                       box in (XBOX(1), YBOX(1)), ..., (XBOX(4), YBOX(4)).

## PGQVP -- inquire viewport size and position

          SUBROUTINE PGQVP (UNITS, X1, X2, Y1, Y2)
          INTEGER UNITS
          REAL    X1, X2, Y1, Y2

    Inquiry routine to determine the current viewport setting.
    The values returned may be normalized device coordinates, inches, mm,
    or pixels, depending on the value of the input parameter CFLAG.

    Arguments:
     UNITS  (input)  : used to specify the units of the output parameters:
                       UNITS = 0 : normalized device coordinates
                       UNITS = 1 : inches
                       UNITS = 2 : millimeters
                       UNITS = 3 : pixels
                       Other values give an error message, and are
                       treated as 0.
     X1     (output) : the x-coordinate of the bottom left corner of the
                       viewport.
     X2     (output) : the x-coordinate of the top right corner of the
                       viewport.
     Y1     (output) : the y-coordinate of the bottom left corner of the
                       viewport.
     Y2     (output) : the y-coordinate of the top right corner of the
                       viewport.

## PGQVSZ -- inquire size of view surface

          SUBROUTINE PGQVSZ (UNITS, X1, X2, Y1, Y2)
          INTEGER UNITS
          REAL X1, X2, Y1, Y2

    This routine returns the dimensions of the view surface (the maximum
    plottable area) of the currently selected graphics device, in
    a variety of units. The size of the view surface is device-dependent
    and is established when the graphics device is opened. On some
    devices, it can be changed by calling PGPAP before starting a new
    page with PGPAGE. On some devices, the size can be changed (e.g.,
    by a workstation window manager) outside PGPLOT, and PGPLOT detects
    the change when PGPAGE is used. Call this routine after PGPAGE to
    find the current size.

    Note 1: the width and the height of the view surface in normalized
    device coordinates are both always equal to 1.0.

    Note 2: when the device is divided into panels (see PGSUBP), the
    view surface is a single panel.

    Arguments:
     UNITS  (input)  : 0,1,2,3 for output in normalized device coords,
                       inches, mm, or device units (pixels)
     X1     (output) : always returns 0.0
     X2     (output) : width of view surface
     Y1     (output) : always returns 0.0
     Y2     (output) : height of view surface

## PGQWIN -- inquire window boundary coordinates

          SUBROUTINE PGQWIN (X1, X2, Y1, Y2)
          REAL X1, X2, Y1, Y2

    Inquiry routine to determine the current window setting.
    The values returned are world coordinates.

    Arguments:
     X1     (output) : the x-coordinate of the bottom left corner
                       of the window.
     X2     (output) : the x-coordinate of the top right corner
                       of the window.
     Y1     (output) : the y-coordinate of the bottom left corner
                       of the window.
     Y2     (output) : the y-coordinate of the top right corner
                       of the window.

## PGRECT -- draw a rectangle, using fill-area attributes

          SUBROUTINE PGRECT (X1, X2, Y1, Y2)
          REAL X1, X2, Y1, Y2

    This routine can be used instead of PGPOLY for the special case of
    drawing a rectangle aligned with the coordinate axes; only two
    vertices need be specified instead of four.  On most devices, it is
    faster to use PGRECT than PGPOLY for drawing rectangles.  The
    rectangle has vertices at (X1,Y1), (X1,Y2), (X2,Y2), and (X2,Y1).

    Arguments:
     X1, X2 (input) : the horizontal range of the rectangle.
     Y1, Y2 (input) : the vertical range of the rectangle.

## PGRND -- find the smallest `round' number greater than x

          REAL FUNCTION PGRND (X, NSUB)
          REAL X
          INTEGER NSUB

    Routine to find the smallest "round" number larger than x, a
    "round" number being 1, 2 or 5 times a power of 10. If X is negative,
    PGRND(X) = -PGRND(ABS(X)). eg PGRND(8.7) = 10.0,
    PGRND(-0.4) = -0.5.  If X is zero, the value returned is zero.
    This routine is used by PGBOX for choosing  tick intervals.

    Returns:
     PGRND         : the "round" number.
    Arguments:
     X      (input)  : the number to be rounded.
     NSUB   (output) : a suitable number of subdivisions for
                       subdividing the "nice" number: 2 or 5.

## PGRNGE -- choose axis limits

          SUBROUTINE PGRNGE (X1, X2, XLO, XHI)
          REAL X1, X2, XLO, XHI

    Choose plotting limits XLO and XHI which encompass the data
    range X1 to X2.

    Arguments:
     X1, X2 (input)  : the data range (X1<X2), ie, the min and max values
                       to be plotted.
     XLO, XHI (output) : suitable values to use as the extremes of a graph
                       axis (XLO <= X1, XHI >= X2).

## PGSAH -- set arrow-head style

          SUBROUTINE PGSAH (FS, ANGLE, BARB)
          INTEGER  FS
          REAL ANGLE, BARB

    Set the style to be used for arrowheads drawn with routine PGARRO.

    Argument:
     FS     (input)  : FS = 1 => filled; FS = 2 => outline.
                       Other values are treated as 2. Default 1.
     ANGLE  (input)  : the acute angle of the arrow point, in degrees;
                       angles in the range 20.0 to 90.0 give reasonable
                       results. Default 45.0.
     BARB   (input)  : the fraction of the triangular arrow-head that
                       is cut away from the back. 0.0 gives a triangular
                       wedge arrow-head; 1.0 gives an open >. Values 0.3
                       to 0.7 give reasonable results. Default 0.3.

## PGSAVE -- save PGPLOT attributes

          SUBROUTINE PGSAVE

    This routine saves the current PGPLOT attributes in a private storage
    area. They can be restored by calling PGUNSA (unsave). Attributes
    saved are: character font, character height, color index, fill-area
    style, line style, line width, pen position, arrow-head style,
    hatching style, and clipping state. Color representation is not saved.

    Calls to PGSAVE and PGUNSA should always be paired. Up to 20 copies
    of the attributes may be saved. PGUNSA always retrieves the last-saved
    values (last-in first-out stack).

    Note that when multiple devices are in use, PGUNSA retrieves the
    values saved by the last PGSAVE call, even if they were for a
    different device.

    Arguments: none

## PGUNSA -- restore PGPLOT attributes

          ENTRY PGUNSA

    This routine restores the PGPLOT attributes saved in the last call to
    PGSAVE. Usage: CALL PGUNSA (no arguments). See PGSAVE.

    Arguments: none

## PGSCF -- set character font

          SUBROUTINE PGSCF (FONT)
          INTEGER  FONT

    Set the Character Font for subsequent text plotting. Four different
    fonts are available:
      1: (default) a simple single-stroke font ("normal" font)
      2: roman font
      3: italic font
      4: script font
    This call determines which font is in effect at the beginning of
    each text string. The font can be changed (temporarily) within a text
    string by using the escape sequences \fn, \fr, \fi, and \fs for fonts
    1, 2, 3, and 4, respectively.

    Argument:
     FONT   (input)  : the font number to be used for subsequent text
                       plotting (in range 1-4).

## PGSCH -- set character height

          SUBROUTINE PGSCH (SIZE)
          REAL SIZE

    Set the character size attribute. The size affects all text and graph
    markers drawn later in the program. The default character size is
    1.0, corresponding to a character height about 1/40 the height of
    the view surface.  Changing the character size also scales the length
    of tick marks drawn by PGBOX and terminals drawn by PGERRX and PGERRY.

    Argument:
     SIZE   (input)  : new character size (dimensionless multiple of
                       the default size).

## PGSCI -- set color index

          SUBROUTINE PGSCI (CI)
          INTEGER  CI

    Set the Color Index for subsequent plotting, if the output device
    permits this. The default color index is 1, usually white on a black
    background for video displays or black on a white background for
    printer plots. The color index is an integer in the range 0 to a
    device-dependent maximum. Color index 0 corresponds to the background
    color; lines may be "erased" by overwriting them with color index 0
    (if the device permits this).

    If the requested color index is not available on the selected device,
    color index 1 will be substituted.

    The assignment of colors to color indices can be changed with
    subroutine PGSCR (set color representation).  Color indices 0-15
    have predefined color representations (see the PGPLOT manual), but
    these may be changed with PGSCR.  Color indices above 15  have no
    predefined representations: if these indices are used, PGSCR must
    be called to define the representation.

    Argument:
     CI     (input)  : the color index to be used for subsequent plotting
                       on the current device (in range 0-max). If the
                       index exceeds the device-dependent maximum, the
                       default color index (1) is used.

## PGSCIR -- set color index range

          SUBROUTINE PGSCIR(ICILO, ICIHI)
          INTEGER   ICILO, ICIHI

    Set the color index range to be used for producing images with
    PGGRAY or PGIMAG. If the range is not all within the range supported
    by the device, a smaller range will be used. The number of
    different colors available for images is ICIHI-ICILO+1.

    Arguments:
     ICILO  (input)  : the lowest color index to use for images
     ICIHI  (input)  : the highest color index to use for images

## PGSCLP -- enable or disable clipping at edge of viewport

          SUBROUTINE PGSCLP(STATE)
          INTEGER STATE

    Normally all PGPLOT primitives except text are ``clipped'' at the
    edge of the viewport: parts of the primitives that lie outside
    the viewport are not drawn. If clipping is disabled by calling this
    routine, primitives are visible wherever they lie on the view
    surface. The default (clipping enabled) is appropriate for almost
    all applications.

    Argument:
     STATE  (input)  : 0 to disable clipping, or 1 to enable clipping.

    25-Feb-1997 [TJP] - new routine.

## PGSCR -- set color representation

          SUBROUTINE PGSCR (CI, CR, CG, CB)
          INTEGER CI
          REAL    CR, CG, CB

    Set color representation: i.e., define the color to be
    associated with a color index.  Ignored for devices which do not
    support variable color or intensity.  Color indices 0-15
    have predefined color representations (see the PGPLOT manual), but
    these may be changed with PGSCR.  Color indices 16-maximum have no
    predefined representations: if these indices are used, PGSCR must
    be called to define the representation. On monochrome output
    devices (e.g. VT125 terminals with monochrome monitors), the
    monochrome intensity is computed from the specified Red, Green, Blue
    intensities as 0.30*R + 0.59*G + 0.11*B, as in US color television
    systems, NTSC encoding.  Note that most devices do not have an
    infinite range of colors or monochrome intensities available;
    the nearest available color is used.  Examples: for black,
    set CR=CG=CB=0.0; for white, set CR=CG=CB=1.0; for medium gray,
    set CR=CG=CB=0.5; for medium yellow, set CR=CG=0.5, CB=0.0.

    Argument:
     CI     (input)  : the color index to be defined, in the range 0-max.
                       If the color index greater than the device
                       maximum is specified, the call is ignored. Color
                       index 0 applies to the background color.
     CR     (input)  : red, green, and blue intensities,
     CG     (input)    in range 0.0 to 1.0.
     CB     (input)

## PGSCRL -- scroll window

          SUBROUTINE PGSCRL (DX, DY)
          REAL DX, DY

    This routine moves the window in world-coordinate space while
    leaving the viewport unchanged. On devices that have the
    capability, the pixels within the viewport are scrolled
    horizontally, vertically or both in such a way that graphics
    previously drawn in the window are shifted so that their world
    coordinates are unchanged.

    If the old window coordinate range was (X1, X2, Y1, Y2), the new
    coordinate range will be approximately (X1+DX, X2+DX, Y1+DY, Y2+DY).
    The size and scale of the window are unchanged.

    Thee window can only be shifted by a whole number of pixels
    (device coordinates). If DX and DY do not correspond to integral
    numbers of pixels, the shift will be slightly different from that
    requested. The new window-coordinate range, and hence the exact
    amount of the shift, can be determined by calling PGQWIN after this
    routine.

    Pixels that are moved out of the viewport by this operation are
    lost completely; they cannot be recovered by scrolling back.
    Pixels that are ``scrolled into'' the viewport are filled with
    the background color (color index 0).

    If the absolute value of DX is bigger than the width of the window,
    or the aboslute value of DY is bigger than the height of the window,
    the effect will be the same as zeroing all the pixels in the
    viewport.

    Not all devices have the capability to support this routine.
    It is only available on some interactive devices that have discrete
    pixels. To determine whether the current device has scroll capability,
    call PGQINF.

    Arguments:
     DX     (input)  : distance (in world coordinates) to shift the
                       window horizontally (positive shifts window to the
                       right and scrolls to the left).
     DY     (input)  : distance (in world coordinates) to shift the
                       window vertically (positive shifts window up and
                       scrolls down).

## PGSCRN -- set color representation by name

          SUBROUTINE PGSCRN(CI, NAME, IER)
          INTEGER CI
          CHARACTER*(*) NAME
          INTEGER IER

    Set color representation: i.e., define the color to be
    associated with a color index.  Ignored for devices which do not
    support variable color or intensity.  This is an alternative to
    routine PGSCR. The color representation is defined by name instead
    of (R,G,B) components.

    Color names are defined in an external file which is read the first
    time that PGSCRN is called. The name of the external file is
    found as follows:
    1. if environment variable (logical name) PGPLOT_RGB is defined,
       its value is used as the file name;
    2. otherwise, if environment variable PGPLOT_DIR is defined, a
       file "rgb.txt" in the directory named by this environment
       variable is used;
    3. otherwise, file "rgb.txt" in the current directory is used.
    If all of these fail to find a file, an error is reported and
    the routine does nothing.

    Each line of the file
    defines one color, with four blank- or tab-separated fields per
    line. The first three fields are the R, G, B components, which
    are integers in the range 0 (zero intensity) to 255 (maximum
    intensity). The fourth field is the color name. The color name
    may include embedded blanks. Example:

    255   0   0 red
    255 105 180 hot pink
    255 255 255 white
      0   0   0 black

    Arguments:
     CI     (input)  : the color index to be defined, in the range 0-max.
                       If the color index greater than the device
                       maximum is specified, the call is ignored. Color
                       index 0 applies to the background color.
     NAME   (input)  : the name of the color to be associated with
                       this color index. This name must be in the
                       external file. The names are not case-sensitive.
                       If the color is not listed in the file, the
                       color representation is not changed.
     IER    (output) : returns 0 if the routine was successful, 1
                       if an error occurred (either the external file
                       could not be read, or the requested color was
                       not defined in the file).

## PGSFS -- set fill-area style

          SUBROUTINE PGSFS (FS)
          INTEGER  FS

    Set the Fill-Area Style attribute for subsequent area-fill by
    PGPOLY, PGRECT, or PGCIRC.  Four different styles are available:
    solid (fill polygon with solid color of the current color-index),
    outline (draw outline of polygon only, using current line attributes),
    hatched (shade interior of polygon with parallel lines, using
    current line attributes), or cross-hatched. The orientation and
    spacing of hatch lines can be specified with routine PGSHS (set
    hatch style).

    Argument:
     FS     (input)  : the fill-area style to be used for subsequent
                       plotting:
                         FS = 1 => solid (default)
                         FS = 2 => outline
                         FS = 3 => hatched
                         FS = 4 => cross-hatched
                       Other values give an error message and are
                       treated as 2.

## PGSHLS -- set color representation using HLS system

          SUBROUTINE PGSHLS (CI, CH, CL, CS)
          INTEGER CI
          REAL    CH, CL, CS

    Set color representation: i.e., define the color to be
    associated with a color index.  This routine is equivalent to
    PGSCR, but the color is defined in the Hue-Lightness-Saturation
    model instead of the Red-Green-Blue model. Hue is represented
    by an angle in degrees, with red at 120, green at 240,
    and blue at 0 (or 360). Lightness ranges from 0.0 to 1.0, with black
    at lightness 0.0 and white at lightness 1.0. Saturation ranges from
    0.0 (gray) to 1.0 (pure color). Hue is irrelevant when saturation
    is 0.0.

    Examples:           H     L     S        R     G     B
        black          any   0.0   0.0      0.0   0.0   0.0
        white          any   1.0   0.0      1.0   1.0   1.0
        medium gray    any   0.5   0.0      0.5   0.5   0.5
        red            120   0.5   1.0      1.0   0.0   0.0
        yellow         180   0.5   1.0      1.0   1.0   0.0
        pink           120   0.7   0.8      0.94  0.46  0.46

    Reference: SIGGRAPH Status Report of the Graphic Standards Planning
    Committee, Computer Graphics, Vol.13, No.3, Association for
    Computing Machinery, New York, NY, 1979. See also: J. D. Foley et al,
    ``Computer Graphics: Principles and Practice'', second edition,
    Addison-Wesley, 1990, section 13.3.5.

    Argument:
     CI     (input)  : the color index to be defined, in the range 0-max.
                       If the color index greater than the device
                       maximum is specified, the call is ignored. Color
                       index 0 applies to the background color.
     CH     (input)  : hue, in range 0.0 to 360.0.
     CL     (input)  : lightness, in range 0.0 to 1.0.
     CS     (input)  : saturation, in range 0.0 to 1.0.

## PGSHS -- set hatching style

          SUBROUTINE PGSHS (ANGLE, SEPN, PHASE)
          REAL ANGLE, SEPN, PHASE

    Set the style to be used for hatching (fill area with fill-style 3).
    The default style is ANGLE=45.0, SEPN=1.0, PHASE=0.0.

    Arguments:
     ANGLE  (input)  : the angle the hatch lines make with the
                       horizontal, in degrees, increasing
                       counterclockwise (this is an angle on the
                       view surface, not in world-coordinate space).
     SEPN   (input)  : the spacing of the hatch lines. The unit spacing
                       is 1 percent of the smaller of the height or
                       width of the view surface. This should not be
                       zero.
     PHASE  (input)  : a real number between 0 and 1; the hatch lines
                       are displaced by this fraction of SEPN from a
                       fixed reference.  Adjacent regions hatched with the
                       same PHASE have contiguous hatch lines. To hatch
                       a region with alternating lines of two colors,
                       fill the area twice, with PHASE=0.0 for one color
                       and PHASE=0.5 for the other color.

## PGSITF -- set image transfer function

          SUBROUTINE PGSITF (ITF)
          INTEGER  ITF

    Set the Image Transfer Function for subsequent images drawn by
    PGIMAG, PGGRAY, or PGWEDG. The Image Transfer Function is used
    to map array values into the available range of color indices
    specified with routine PGSCIR or (for PGGRAY on some devices)
    into dot density.

    Argument:
     ITF    (input)  : type of transfer function:
                         ITF = 0 : linear
                         ITF = 1 : logarithmic
                         ITF = 2 : square-root

## PGSLCT -- select an open graphics device

          SUBROUTINE PGSLCT(ID)
          INTEGER ID

    Select one of the open graphics devices and direct subsequent
    plotting to it. The argument is the device identifier returned by
    PGOPEN when the device was opened. If the supplied argument is not a
    valid identifier of an open graphics device, a warning message is
    issued and the current selection is unchanged.

    [This routine was added to PGPLOT in Version 5.1.0.]

    Arguments:

    ID (input, integer): identifier of the device to be selected.

## PGSLS -- set line style

          SUBROUTINE PGSLS (LS)
          INTEGER  LS

    Set the line style attribute for subsequent plotting. This
    attribute affects line primitives only; it does not affect graph
    markers, text, or area fill.
    Five different line styles are available, with the following codes:
    1 (full line), 2 (dashed), 3 (dot-dash-dot-dash), 4 (dotted),
    5 (dash-dot-dot-dot). The default is 1 (normal full line).

    Argument:
     LS     (input)  : the line-style code for subsequent plotting
                       (in range 1-5).

## PGSLW -- set line width

          SUBROUTINE PGSLW (LW)
          INTEGER  LW

    Set the line-width attribute. This attribute affects lines, graph
    markers, and text. The line width is specified in units of 1/200
    (0.005) inch (about 0.13 mm) and must be an integer in the range
    1-201. On some devices, thick lines are generated by tracing each
    line with multiple strokes offset in the direction perpendicular to
    the line.

    Argument:
     LW     (input)  : width of line, in units of 0.005 inch (0.13 mm)
                       in range 1-201.

## PGSTBG -- set text background color index

          SUBROUTINE PGSTBG (TBCI)
          INTEGER  TBCI

    Set the Text Background Color Index for subsequent text. By default
    text does not obscure underlying graphics. If the text background
    color index is positive, however, text is opaque: the bounding box
    of the text is filled with the color specified by PGSTBG before
    drawing the text characters in the current color index set by PGSCI.
    Use color index 0 to erase underlying graphics before drawing text.

    Argument:
     TBCI   (input)  : the color index to be used for the background
                       for subsequent text plotting:
                         TBCI < 0  => transparent (default)
                         TBCI >= 0 => text will be drawn on an opaque
                       background with color index TBCI.

## PGSUBP -- subdivide view surface into panels

          SUBROUTINE PGSUBP (NXSUB, NYSUB)
          INTEGER NXSUB, NYSUB

    PGPLOT divides the physical surface of the plotting device (screen,
    window, or sheet of paper) into NXSUB x NYSUB `panels'. When the
    view surface is sub-divided in this way, PGPAGE moves to the next
    panel, not the next physical page. The initial subdivision of the
    view surface is set in the call to PGBEG. When PGSUBP is called,
    it forces the next call to PGPAGE to start a new physical page,
    subdivided in the manner indicated. No plotting should be done
    between a call of PGSUBP and a call of PGPAGE (or PGENV, which calls
    PGPAGE).

    If NXSUB > 0, PGPLOT uses the panels in row order; if <0,
    PGPLOT uses them in column order, e.g.,

     NXSUB=3, NYSUB=2            NXSUB=-3, NYSUB=2

    +-----+-----+-----+         +-----+-----+-----+
    |  1  |  2  |  3  |         |  1  |  3  |  5  |
    +-----+-----+-----+         +-----+-----+-----+
    |  4  |  5  |  6  |         |  2  |  4  |  6  |
    +-----+-----+-----+         +-----+-----+-----+

    PGPLOT advances from one panels to the next when PGPAGE is called,
    clearing the screen or starting a new page when the last panel has
    been used. It is also possible to jump from one panel to another
    in random order by calling PGPANL.

    Arguments:
     NXSUB  (input)  : the number of subdivisions of the view surface in
                       X (>0 or <0).
     NYSUB  (input)  : the number of subdivisions of the view surface in
                       Y (>0).

## PGSVP -- set viewport (normalized device coordinates)

          SUBROUTINE PGSVP (XLEFT, XRIGHT, YBOT, YTOP)
          REAL XLEFT, XRIGHT, YBOT, YTOP

    Change the size and position of the viewport, specifying
    the viewport in normalized device coordinates.  Normalized
    device coordinates run from 0 to 1 in each dimension. The
    viewport is the rectangle on the view surface "through"
    which one views the graph.  All the PG routines which plot lines
    etc. plot them within the viewport, and lines are truncated at
    the edge of the viewport (except for axes, labels etc drawn with
    PGBOX or PGLAB).  The region of world space (the coordinate
    space of the graph) which is visible through the viewport is
    specified by a call to PGSWIN.  It is legal to request a
    viewport larger than the view surface; only the part which
    appears on the view surface will be plotted.

    Arguments:
     XLEFT  (input)  : x-coordinate of left hand edge of viewport, in NDC.
     XRIGHT (input)  : x-coordinate of right hand edge of viewport,
                       in NDC.
     YBOT   (input)  : y-coordinate of bottom edge of viewport, in NDC.
     YTOP   (input)  : y-coordinate of top  edge of viewport, in NDC.

## PGSWIN -- set window

          SUBROUTINE PGSWIN (X1, X2, Y1, Y2)
          REAL X1, X2, Y1, Y2

    Change the window in world coordinate space that is to be mapped on
    to the viewport.  Usually PGSWIN is called automatically by PGENV,
    but it may be called directly by the user.

    Arguments:
     X1     (input)  : the x-coordinate of the bottom left corner
                       of the viewport.
     X2     (input)  : the x-coordinate of the top right corner
                       of the viewport (note X2 may be less than X1).
     Y1     (input)  : the y-coordinate of the bottom left corner
                       of the viewport.
     Y2     (input)  : the y-coordinate of the top right corner
                       of the viewport (note Y2 may be less than Y1).

## PGTBOX -- draw frame and write (DD) HH MM SS.S labelling

          SUBROUTINE PGTBOX (XOPT, XTICK, NXSUB, YOPT, YTICK, NYSUB)

          REAL XTICK, YTICK
          INTEGER NXSUB, NYSUB
          CHARACTER XOPT*(*), YOPT*(*)

    Draw a box and optionally label one or both axes with (DD) HH MM SS
    style numeric labels (useful for time or RA - DEC plots).   If this
    style of labelling is desired, then PGSWIN should have been called
    previously with the extrema in SECONDS of time.

    In the seconds field, you can have at most 3 places after the decimal
    point, so that 1 ms is the smallest time interval you can time label.

    Large numbers are coped with by fields of 6 characters long.  Thus
    you could have times with days or hours as big as 999999.  However,
    in practice, you might have trouble with labels overwriting  themselves
    with such large numbers unless you a) use a small time INTERVAL,
    b) use a small character size or c) choose your own sparse ticks in
    the call to PGTBOX.

    PGTBOX will attempt, when choosing its own ticks, not to overwrite
    the labels, but this algorithm is not very bright and may fail.

    Note that small intervals but large absolute times such as
    TMIN = 200000.0 s and TMAX=200000.1 s will cause the algorithm
    to fail.  This is inherent in PGPLOT's use of single precision
    and cannot be avoided.  In such cases, you should use relative
    times if possible.

    PGTBOX's labelling philosophy is that the left-most or bottom tick of
    the axis contains a full label.  Thereafter, only changing fields are
    labelled.  Negative fields are given a '-' label, positive fields
    have none.   Axes that have the DD (or HH if the day field is not
    used) field on each major tick carry the sign on each field.  If the
    axis crosses zero, the zero tick will carry a full label and sign.

    This labelling style can cause a little confusion with some special
    cases, but as long as you know its philosophy, the truth can be divined.
    Consider an axis with TMIN=20s, TMAX=-20s.   The labels will look like

           +----------+----------+----------+----------+
        0h0m20s      10s      -0h0m0s      10s        20s

    Knowing that the left field always has a full label and that
    positive fields are unsigned, informs that time is decreasing
    from left to right, not vice versa.   This can become very
    unclear if you have used the 'F' option, but that is your problem !

    Exceptions to this labelling philosophy are when the finest time
    increment being displayed is hours (with option 'Y') or days.
    Then all fields carry a label.  For example,

           +----------+----------+----------+----------+
         -10h        -8h        -6h        -4h        -2h

    PGTBOX can be used in place of PGBOX; it calls PGBOX and only invokes
    time labelling if requested. Other options are passed intact to PGBOX.

    Inputs:
     XOPT   :  X-options for PGTBOX.  Same as for PGBOX plus

                'Z' for (DD) HH MM SS.S time labelling
                'Y' means don't include the day field so that labels
                    are HH MM SS.S rather than DD HH MM SS.S   The hours
                    will accumulate beyond 24 if necessary in this case.
                'X' label the HH field as modulo 24.  Thus, a label
                    such as 25h 10m would come out as 1h 10m
                'H' means superscript numbers with d, h, m, & s  symbols
                'D' means superscript numbers with    o, ', & '' symbols
                'F' causes the first label (left- or bottom-most) to
                    be omitted. Useful for sub-panels that abut each other.
                    Care is needed because first label carries sign as well.
                'O' means omit leading zeros in numbers < 10
                    E.g.  3h 3m 1.2s rather than 03h 03m 01.2s  Useful
                    to help save space on X-axes. The day field does not
                    use this facility.

     YOPT   :  Y-options for PGTBOX.  See above.
     XTICK  :  X-axis major tick increment.  0.0 for default.
     YTICK  :  Y-axis major tick increment.  0.0 for default.
               If the 'Z' option is used then XTICK and/or YTICK must
               be in seconds.
     NXSUB  :  Number of intervals for minor ticks on X-axis. 0 for default
     NYSUB  :  Number of intervals for minor ticks on Y-axis. 0 for default

     The regular XOPT and YOPT axis options for PGBOX are

     A : draw Axis (X axis is horizontal line Y=0, Y axis is vertical
         line X=0).
     B : draw bottom (X) or left (Y) edge of frame.
     C : draw top (X) or right (Y) edge of frame.
     G : draw Grid of vertical (X) or horizontal (Y) lines.
     I : Invert the tick marks; ie draw them outside the viewport
         instead of inside.
     L : label axis Logarithmically (see below).
     N : write Numeric labels in the conventional location below the
         viewport (X) or to the left of the viewport (Y).
     P : extend ("Project") major tick marks outside the box (ignored if
         option I is specified).
     M : write numeric labels in the unconventional location above the
         viewport (X) or to the right of the viewport (Y).
     T : draw major Tick marks at the major coordinate interval.
     S : draw minor tick marks (Subticks).
     V : orient numeric labels Vertically. This is only applicable to Y.
         The default is to write Y-labels parallel to the axis.
     1 : force decimal labelling, instead of automatic choice (see PGNUMB).
     2 : force exponential labelling, instead of automatic.

         The default is to write Y-labels parallel to the axis

           ******************        EXCEPTIONS       *******************

           Note that
             1) PGBOX option 'L' (log labels) is ignored with option 'Z'
             2) The 'O' option will be ignored for the 'V' option as it
                makes it impossible to align the labels nicely
             3) Option 'Y' is forced with option 'D'

           ***************************************************************

## PGTEXT -- write text (horizontal, left-justified)

          SUBROUTINE PGTEXT (X, Y, TEXT)
          REAL X, Y
          CHARACTER*(*) TEXT

    Write text. The bottom left corner of the first character is placed
    at the specified position, and the text is written horizontally.
    This is a simplified interface to the primitive routine PGPTXT.
    For non-horizontal text, use PGPTXT.

    Arguments:
     X      (input)  : world x-coordinate of start of string.
     Y      (input)  : world y-coordinate of start of string.
     TEXT   (input)  : the character string to be plotted.

## PGTICK -- draw a single tick mark on an axis

          SUBROUTINE PGTICK (X1, Y1, X2, Y2, V, TIKL, TIKR, DISP,
         :                   ORIENT, STR)
          REAL X1, Y1, X2, Y2, V, TIKL, TIKR, DISP, ORIENT
          CHARACTER*(*) STR

    Draw and label single tick mark on a graph axis. The tick mark is
    a short line perpendicular to the direction of the axis (which is not
    drawn by this routine). The optional text label is drawn with its
    baseline parallel to the axis and reading in the same direction as
    the axis (from point 1 to point 2). Current line and text attributes
    are used.

    Arguments:
     X1, Y1 (input)  : world coordinates of one endpoint of the axis.
     X2, Y2 (input)  : world coordinates of the other endpoint of the axis.
     V      (input)  : draw the tick mark at fraction V (0<=V<=1) along
                       the line from (X1,Y1) to (X2,Y2).
     TIKL   (input)  : length of tick mark drawn to left of axis
                       (as seen looking from first endpoint to second), in
                       units of the character height.
     TIKR   (input)  : length of major tick marks drawn to right of axis,
                       in units of the character height.
     DISP   (input)  : displacement of label text to
                       right of axis, in units of the character height.
     ORIENT (input)  : orientation of label text, in degrees; angle between
                       baseline of text and direction of axis (0-360°).
     STR    (input)  : text of label (may be blank).

## PGUPDT -- update display

          SUBROUTINE PGUPDT

    Update the graphics display: flush any pending commands to the
    output device. This routine empties the buffer created by PGBBUF,
    but it does not alter the PGBBUF/PGEBUF counter. The routine should
    be called when it is essential that the display be completely up to
    date (before interaction with the user, for example) but it is not
    known if output is being buffered.

    Arguments: none

## PGVECT -- vector map of a 2D data array, with blanking

          SUBROUTINE PGVECT (A, B, IDIM, JDIM, I1, I2, J1, J2, C, NC, TR,
         1                   BLANK)
          INTEGER IDIM, JDIM, I1, I2, J1, J2, NC
          REAL    A(IDIM,JDIM), B(IDIM, JDIM), TR(6), BLANK, C

    Draw a vector map of two arrays.  This routine is similar to
    PGCONB in that array elements that have the "magic value" defined by
    the argument BLANK are ignored, making gaps in the vector map.  The
    routine may be useful for data measured on most but not all of the
    points of a grid. Vectors are displayed as arrows; the style of the
    arrowhead can be set with routine PGSAH, and the the size of the
    arrowhead is determined by the current character size, set by PGSCH.

    Arguments:
     A      (input)  : horizontal component data array.
     B      (input)  : vertical component data array.
     IDIM   (input)  : first dimension of A and B.
     JDIM   (input)  : second dimension of A and B.
     I1,I2  (input)  : range of first index to be mapped (inclusive).
     J1,J2  (input)  : range of second index to be mapped (inclusive).
     C      (input)  : scale factor for vector lengths, if 0.0, C will be
                       set so that the longest vector is equal to the
                       smaller of TR(2)+TR(3) and TR(5)+TR(6).
     NC     (input)  : vector positioning code.
                       <0 vector head positioned on coordinates
                       >0 vector base positioned on coordinates
                       =0 vector centered on the coordinates
     TR     (input)  : array defining a transformation between the I,J
                       grid of the array and the world coordinates. The
                       world coordinates of the array point A(I,J) are
                       given by:
                         X = TR(1) + TR(2)*I + TR(3)*J
                         Y = TR(4) + TR(5)*I + TR(6)*J
                       Usually TR(3) and TR(5) are zero - unless the
                       coordinate transformation involves a rotation
                       or shear.
     BLANK   (input) : elements of arrays A or B that are exactly equal to
                       this value are ignored (blanked).

## PGVPORT -- non-standard alias for PGSVP

          SUBROUTINE PGVPORT (XLEFT, XRIGHT, YBOT, YTOP)
          REAL XLEFT, XRIGHT, YBOT, YTOP

    See description of PGSVP.

## PGVSIZ -- set viewport (inches)

          SUBROUTINE PGVSIZ (XLEFT, XRIGHT, YBOT, YTOP)
          REAL XLEFT, XRIGHT, YBOT, YTOP

    Change the size and position of the viewport, specifying
    the viewport in physical device coordinates (inches).  The
    viewport is the rectangle on the view surface "through"
    which one views the graph.  All the PG routines which plot lines
    etc. plot them within the viewport, and lines are truncated at
    the edge of the viewport (except for axes, labels etc drawn with
    PGBOX or PGLAB).  The region of world space (the coordinate
    space of the graph) which is visible through the viewport is
    specified by a call to PGSWIN.  It is legal to request a
    viewport larger than the view surface; only the part which
    appears on the view surface will be plotted.

    Arguments:
     XLEFT  (input)  : x-coordinate of left hand edge of viewport, in
                       inches from left edge of view surface.
     XRIGHT (input)  : x-coordinate of right hand edge of viewport, in
                       inches from left edge of view surface.
     YBOT   (input)  : y-coordinate of bottom edge of viewport, in
                       inches from bottom of view surface.
     YTOP   (input)  : y-coordinate of top  edge of viewport, in inches
                       from bottom of view surface.

## PGVSIZE -- non-standard alias for PGVSIZ

          SUBROUTINE PGVSIZE (XLEFT, XRIGHT, YBOT, YTOP)
          REAL XLEFT, XRIGHT, YBOT, YTOP

    See description of PGVSIZ.

## PGVSTAND -- non-standard alias for PGVSTD

          SUBROUTINE PGVSTAND

    See description of PGVSTD.

## PGVSTD -- set standard (default) viewport

          SUBROUTINE PGVSTD

    Define the viewport to be the standard viewport.  The standard
    viewport is the full area of the view surface (or panel),
    less a margin of 4 character heights all round for labelling.
    It thus depends on the current character size, set by PGSCH.

    Arguments: none.

## PGWEDG -- annotate an image plot with a wedge

          SUBROUTINE PGWEDG(SIDE, DISP, WIDTH, FG, BG, LABEL)
          CHARACTER *(*) SIDE,LABEL
          REAL DISP, WIDTH, FG, BG

    Plot an annotated grey-scale or color wedge parallel to a given axis
    of the the current viewport. This routine is designed to provide a
    brightness/color scale for an image drawn with PGIMAG or PGGRAY.
    The wedge will be drawn with the transfer function set by PGSITF
    and using the color index range set by PGSCIR.

    Arguments:
     SIDE   (input)  : The first character must be one of the characters
                       'B', 'L', 'T', or 'R' signifying the Bottom, Left,
                       Top, or Right edge of the viewport.
                       The second character should be 'I' to use PGIMAG
                       to draw the wedge, or 'G' to use PGGRAY.
     DISP   (input)  : the displacement of the wedge from the specified
                       edge of the viewport, measured outwards from the
                       viewport in units of the character height. Use a
                       negative value to write inside the viewport, a
                       positive value to write outside.
     WIDTH  (input)  : The total width of the wedge including annotation,
                       in units of the character height.
     FG     (input)  : The value which is to appear with shade
                       1 ("foreground"). Use the values of FG and BG
                       that were supplied to PGGRAY or PGIMAG.
     BG     (input)  : the value which is to appear with shade
                       0 ("background").
     LABEL  (input)  : Optional units label. If no label is required
                       use ' '.

## PGWINDOW -- non-standard alias for PGSWIN

          SUBROUTINE PGWINDOW (X1, X2, Y1, Y2)
          REAL X1, X2, Y1, Y2

    See description of PGSWIN.

## PGWNAD -- set window and adjust viewport to same aspect ratio

          SUBROUTINE PGWNAD (X1, X2, Y1, Y2)
          REAL X1, X2, Y1, Y2

    Change the window in world coordinate space that is to be mapped on
    to the viewport, and simultaneously adjust the viewport so that the
    world-coordinate scales are equal in x and y. The new viewport is
    the largest one that can fit within the previously set viewport
    while retaining the required aspect ratio.

    Arguments:
     X1     (input)  : the x-coordinate of the bottom left corner
                       of the viewport.
     X2     (input)  : the x-coordinate of the top right corner
                       of the viewport (note X2 may be less than X1).
     Y1     (input)  : the y-coordinate of the bottom left corner
                       of the viewport.
     Y2     (input)  : the y-coordinate of the top right corner of the
                       viewport (note Y2 may be less than Y1).