3D Plots

After having made a grid you can plot a 3D graph using the command

mesh(xx,yy,z)

where xx and yy are the matrices made by meshgrid and where z is a function of x and y. You get the function values of z by using element by element operations on matrices xx and yy.

>>> x=linspace(-2,2,5);
>>> y=linspace(-2,2,5);
>>> [xx,yy]=meshgrid(x,y);
>>> mesh(xx,yy,4-(xx.^2+yy.^2))

If you want a smoother graph, make a longer x-vector and a longer y-vector.

>>> x=linspace(-2,2,50);
>>> y=linspace(-2,2,50);
>>> [xx,yy]=meshgrid(x,y);
>>> mesh(xx,yy,4-(xx.^2+yy.^2))

You can get a contour plot by using the command meshc.

>>> x=linspace(-2,2,50);
>>> y=linspace(-2,2,50);
>>> [xx,yy]=meshgrid(x,y);
>>> meshc(xx,yy,4-(xx.^2+yy.^2))