x = (-2:0.1:2);
y = x;
[X,Y] = meshgrid(x,y);
f = sin(2 * X) .* cos(3 * Y);

f_noisy = f + 0.2 * randn(size(f));
surf(X,Y,f);
hold on
scatter3(X(:),Y(:),f_noisy(:));