clf
x=-4:4;y=x;x09x09x09x09
[X,Y]=meshgrid(x,y);x09
Z=sqrt(X.^2+Y.^2);x09x09x09x09)
surf(X,Y,Z);x09x09x09x09
colormap(hot)x09x09x09x09
hold on
stem3(X,Y,Z,'bo')x09x09
hold off
xlabel('x'),ylabel('y'),zlabel('z')
axis([-5,5,-5,5,0,inf])x09
view([-84,21])