Subscripted assignment dimension mismatch error

I'm having this error and unfortunately I can't seem to see what's wrong in it. Here are the dimension of the variables:

ki=150, a=0, b=2, hx=0.1818, c=0, d=5, hy=0.3125, pi=150x1 double

Thank you in advance!

figure(1)
U(1:ki,1:ki)=pi;
[X,Y]=meshgrid(a:hx:b,c:hy:d);
surf(X,Y,U');

Answer 1

[Dave B]

When you write:

U(1:ki,1:ki)=pi;

You're trying to put a 150x1 into a 150x150...Maybe what you intended was:

U(1:ki,1:ki)=repmat(pi,1,150);

It's a little unclear what you're after, but if you want to assign to a 150x150 you should probably give it a 150x150

[Alexandra Roxana]

I want to use surf for a figure. I used the finite element method and I have 2 solutions u1, u2 (150x1 double variables). From u1 I calculate the pressure, noted as pi (which is 150x1 double as well).

For the graph, I want it to be within the domain, a rectangle with a=0, b=2, c=0, d=5, hx is the time step for the x-axis (with a,b), hy is the time step for the y-axis. The graph is for pi.

Unfortunately I have a new error now: Error using surf (line 82)

Data dimensions must agree.

[Alexandra Roxana]

If it is of any help, I can post the whole code.

[Dave B]

You said you calculate pressure from u1, so I'm not sure what the surface is as pressure doesn't depend on u2...

U = repmat(pi,1,ki);

[X,Y] = meshgrid(linspace(a,b,ki),linspace(c,d,ki));

surf(X,Y,U');

For example:

u1=linspace(0,2*pi,100)';
u2=linspace(0,1,100)';
zi=sin(u1);
[u1i,u2i]=meshgrid(u1,u2);
surf(u1i,u2i,repmat(zi,1,numel(u1)))

If you want to form a matrix U out of various combinations of u1 and u2, I think you'll need interpolation (e.g. interp2, scatteredinterpolant, griddedinterpolant)

[Alexandra Roxana]

It's the first time I'm computing something like that, but at least I can see a graph. Thank you!