How to generate a surface by a function defined by two sentences?

I would like to generate a graphic like this:

(I'm using >> [X,Y]= meshgrid(0:0.01:1,0:0.01:1);

surf(X,Y,X.*Y);

colorbar. To generate this figure).

But for a function defined by two sentences:

[Walter Roberson]

z = cos(2*pi*Y);
mask = X>0;
z(mask) = z(mask) + X(mask).^2.5;
surf(X, Y, Z)

[João Micheletti]

It worked, thanks