Name:         PGFUNY

Purpose:      function defined by X = F(Y)

Category:     GRAPHICS

File:         pgplot.src

Author:       T.J. Pearson

Use:          see description below.

Description:

            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

Note:         This subroutine is only callable from Fortran, not from C.

Updates:      Oct 16, 1998: JPT automatically extracted from source.