x=-5:0.5:5;nx=length(x);
y=-10:1:10;ny=length(y);
[X,Y]=meshgrid(x,y);
Z=abs(X)-abs(Y)+abs(X-Y);
figure; surfl(X,Y,Z); grid on;
%figure;contour(Z); grid on;
%figure; contour(X,Y,Z); grid on
xlabel('os x');
ylabel('os y');