Question

Say I have the following script:

u = -5:.2:5;
[X,Y] = meshgrid(u, u);
Z = cos(X).*cos(Y).*exp(-sqrt(X.^2 + Y.^2)/4);
surf(X,Y,Z);

Is there anyway that I can make MatLab plot only parts of the surface? Say, for instance, I just want to plot a single point, or a single grid, what can I do? I thought perhaps to plot a single point I could use:

surf(X(1,1), Y(1,1), Z(1,1))

But then I get the error message:

??? Error using ==> surf at 78
Data dimensions must agree.

I would really appreciate some input/help here. Thanks in advance 🙂

Answer 1

When I try what you tried, I get the following:

surf(X(1,1),Y(1,1),Z(1,1))
Error using surf (line 75) Z must be a matrix, not a scalar or vector.

So the problem is that you can’t do just a point or line using surf, you’d have to use a different function. But you can select subregions

>> ii=1:5;
>> jj=1:20;
>> surf(X(ii,jj),Y(ii,jj),Z(ii,jj))

Another way to do it is to use NaNs as a mask.

>> mask = ones(size(X));
>> mask(1:20, 20:end) = nan;
>> surf(X.*mask, Y.*mask, Z.*mask)

This will make the parts where NANs are present not be displayed.