2D plot of a surface defined by a function using colors
fgrayplot(x,y,f,[strf,rect,nax])
fgrayplot(x,y,f,<opt_args>)
:x,y real row vectors. : :f external of type y=f(x,y). : :<opt_args> This represents a sequence of statements `key1=value1,
key2=value2`,... where key1, key2,... can be one of the following: rect, nax, strf or axesflag and frameflag (see plot2d).
: :strf,rect,nax see plot2d. :
fgrayplot makes a 2D plot of the surface given by z=f(x,y) on a grid defined by x and y. Each rectangle on the grid is filled with a gray or color level depending on the average value of z on the corners of the rectangle.
Enter the command fgrayplot() to see a demo.
t=-1:0.1:1;
`deff`_("[z]=my_surface(x,y)","z=x**2+y**2")
fgrayplot(t,t,my_surface,rect=[-2,-2,2,2])