Here, try something like this:
x = 1:10;
y = -10:10;
[Xm, Ym] = meshgrid(x,y);
Lm = Xm.^2 - Ym.^2;
hdl = surf(Xm, Ym, Lm);
Now, let's get to why you were getting errors: 1. When you create meshgrids, you want to define an entire grid, so you need a range of values for both coordinates. 2. The variables you will use to calculate the z values (dependent on x and y) needs to use the mesh variables, and not the ones you defined earlier. 3. Remember to use element-wise operations in your Lm definition, as you want to collectively apply the operation to all elements (square in this case)
Note: Try out different values of x and y to see what you get. I got desirable results with these values.
Hope this helps. Cheers.
