% This function fmile slices the graph of given function f with
% a plane parallel to the yz plane. It assumes that the function
% has already been graphed on a rectangle [a,b] times [c,d].
% The call is xslice('f',x,y0) where f is given in an mfile, and
% xslice(f, x,y0) when f is an inline function. x is a vector of
% x coordinates which ranges from a to b. y0 is the fixed value of y.
function out = xslice(f, x, y0)
z = feval(f,x,y0);
high = max([z+1,0]);
low = min([z-1,0]);
a = min(x);
b = max(x);
xedge = [a b b a a];
yedge = [y0 y0 y0 y0 y0];
zedge = [low low high high low];
fill3(xedge, yedge, zedge,'r')