Error using mesh, Z must be a matrix

I don't know why, but z won't be registered as a martix even when it calculates it as amtrix.

x=linspace(0,4,2);

y=linspace(0,4,2);

z=sin(pi.*x).*sin(pi.*y);

mesh(x,y,z)

Answer 1

[Mischa Kim]

Espen, use

 x = linspace(0,4,20);
 y = linspace(0,4,20);

 [X,Y] = meshgrid(x,y);  % create a grid of data points
 Z     = sin(pi.*X).*sin(pi.*Y);
 mesh(X,Y,Z)

Z needs to be an n-by-m, just like X and Y.