Function to create surfaces directly

I'm trying to figure out a way of creating surfaces directly with a function. I have the code:

 function V=sketch(f,x1,x2,y1,y2,n)
x=linspace(x1,x2,n); y=linspace(y1,y2,n);
[X,Y]=meshgrid(x,y);
Z=f(X,Y);
surf(X,Y,Z)
grid on, box on, hold on
end

but I keep getting the error that x is undefined, which is not true as I've defined it in the very beginning.

I'm using

sketch((@(x,y)exp(1+0.5.*cos(4*x).*(y-2))),-1,3,0,4,-30)

to sample the graph.

What am I doing wrong?

[Stephen23]

Your function worked for me, without any error. And once I changed the number of points to a positive value it even plotted something:

sketch((@(x,y)exp(1+0.5.*cos(4*x).*(y-2))),-1,3,0,4,30) % note +30.

giving: