delta=0.2; 
D = -2.5:delta:2.5; 
N=20;
[X,Y,Z] = peaks(D);
figure(1)
subplot(1,2,1)
contour(X,Y,Z,N)
axis square
subplot(1,2,2)
contour3(X,Y,Z,N)
axis square
figure(2)
meshc(X,Y,Z)





