Why are my array dimensions being changed?

I have a 3D array cart = s x 3 x p double, where s and p are variables chosen as integers by an optimiser. I'm converting this array to the array sph = s x 3 x p through cart2sph;

[sph(:,1,:), sph(:,2,:), sph(:,3,:)] = cart2sph(cart(:,1,:), cart(:,2,:), cart(:,3,:));

This works fine, unless the case happens to be the optimiser choses to set s = 1. Instead of outputting sph = 1 x 3 x p, it outputs sph = p x 3, which causes issues with my code calling the function I do this in.

It only happens with s, I've tried limiting p to 1 only it seems to run fine, can anyone help?

Answer 1

[Star Strider]

You can add the missing dimension.

Experiment with this:

x1 = rand(3,4);
x2(1,:,:) = x1;

To check:

x1s = size(x1)
x2s = size(x2)

produces:

x1s =
     3     4

x2s =
     1     3     4

You will have to set up the appropriate tests to check the dimensions, then do the assignment.

[Scott Hunter]

I think I did something similar, essentially I checked if s == 1, then permuted the array;

if s == 1
    permute(sph, [3 2 1]);
end

[Star Strider]

That wasn’t in the code you posted, so I didn’t see it.

The optimiser could be using the squeeze function to eliminate the singleton dimensions. If that’s the situation, you would have to add it back.

[Scott Hunter]

No no as in I adder it after your comment, it gave me the idea. Thanks!

[Star Strider]

As always, my pleasure!