YCLIP - Clip a function y(x) defined by linear interpolation of the
uniformly sampled values:  y(fx), y(fx+dx), ..., y(fx+(nx-1)*dx).
Returns the number of samples in the clipped function.

yclip		clip a function y(x) defined by linear interplolation of
		uniformly sampled values

Function Prototype:
int yclip (int nx, float dx, float fx, float y[], float ymin, float ymax,
	float xc[], float yc[]);

Input:
nx		number of x (and y) values
dx		x sampling interval
fx		first x
y		array[nx] of uniformly sampled y(x) values
ymin		minimum y value; must not be greater than ymax
ymax		maximum y value; must not be less than ymin

Output:
xc		array[?] of x values for clipped y(x)
yc		array[?] of y values for clipped y(x)

Returned:	number of samples in output arrays xc and yc

Notes:
The output arrays xc and yc should contain space 2*nx values, which
is the maximum possible number (nc) of xc and yc returned.

Author:  Dave Hale, Colorado School of Mines, 07/03/89