%N pgvect %F $MIR/src/pgvect.f
%D Vector map of a 2D data array, with blanking
%B
      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).
