Problems animating a surf plot.

Hello all, I am employing MATLAB to solve some basic PDEs (transport equation) using various numerical schemes. I have no problem creating a 2-d movie of the solution over time. However, when I try the same trick with surf, I either just get the plot of the final frame, or if I try to index it, I get the error:

Error using surf (line 69) Z must be a matrix, not a scalar or vector.

How can I fix this? Below I've attached my code, I appreciate all the help.

W.U.

[Image Analyst]

Note: REQUIRES SYMBOLIC TOOLBOX (so I can't run it). I've added that to the product list.

Answer 1

[Ced]

The code runs without error. I was not quite sure what you were trying to plot in 3D. I mean, you have one nx x nt matrix. If you index it, you have a vector... how should surf plot that?

My best guess is that you want to do something like this:

U_movie = zeros(size(U_t_x));
U_movie(:,1) = U_t_x(:,1);

h = surf(U_movie);
xlim([0 100])
ylim([0 201 ])
view(74, 34)
title(mytitle)
grid on
M(1) = getframe;

for i=2:Tsteps
    U_movie(:,i) = U_t_x(:,i);
    set(h,'ZData',U_movie);
    M(i) = getframe;
    pause(0.1)
end

There might be a more elegant way of doing this, but it works :).

I don't think the angle is so good, I would also only plot a subset of the points to make the edges less prominent, but I've kept these settings as you had them for now.

Note the usage of the "set" function. It's usually a good practice when updating the data in an otherwise constant plot (instead of recreating the figure over and over), and will speed up the plotting process significantly.

Hope this helps.

[Argento]

Thanks Ced, that does it. I was trying to do exactly what you did but could not figure out who to get surf to plot at every time step. Thanks a lot for the help!