Your question is little bit unclear. I am guessing x & y are varying from -2 to 2 as following ?
x = -2:2; % i.e. x = [-2,-1,0,1,2];
y = -2:2; % i.e. y = [-2,-1,0,1,2];
but you have not mentioned how z is varying ? If z is the distance of (x,y) point from the origin, which is the most usual notation, then please mention that in your question.
Please clarify the above mentioned points, then we will be able to help you.
