%N pgerr1 %F $MIR/src/pgerr1.f
%D Horizontal or vertical error bar
%B
      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.
