# PGPLOT Module: 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