Adding matrices in 4D to 3D

I have a matrix that is 7x7x7x5 at the moment, and now I want to add the last dimension matrices together, making a final matrix 7x7x7 but I'm having trouble making this loop. The matrices I want to add together are A(:,:,k,1:5) for the index k that goes from 1:7.

I can add these in the prompt window like this for example;

A(:,:,1,1)+A(:,:,1,2)+A(:,:,1,3)+A(:,:,1,4)+A(:,:,1,5);

A(:,:,2,1)+A(:,:,2,2)+A(:,:,2,3)+A(:,:,2,4)+A(:,:,2,5);

and so on. But how to I make this in a loop with index k for the 3rd dimension, and another index for the 4th dim?

So far my code looks like this(and I know it exceeds matrix dim, but just to exemplify a bit):

total_hitrate_matris=zeros(7,7,7);
for k = 1:7
    for l=1:5
    total_hitrate_matris(:,:,k)=total_hitrate_matris(:,:,k,l)+hitrate_matris(:,:,k,l+1);
    end
end

Answer 1

[Mohammad Abouali]

total_hitrate_matrix = sum(hitrate_matrix,4)

This adds up the 4th dimension and the resulting matrix would be 7x7x7.

[André Svensson]

Thank you, that was exactly what I wanted. And no loop needed! Much better!

[Mohammad Abouali]

You are welcome. If this concludes your question, would you please accept the answer?

Answer 2

[Geoff Hayes]

André - I think that you have the right idea, it is just how you go about initializing the total_hitrate_matris(:,:,1) which is causing the problem. Taking your above code, we can try the following

 hitrate_matris       = randi(255, 7, 7, 7, 5);
 total_hitrate_matris = zeros(7,7,7);

 for u=1:size(hitrate_matris,3)

     % initialize total_hitrate_matris(:,:,u) and then sum the remaining
     % dimensions
     total_hitrate_matris(:,:,u) = hitrate_matris(:,:,u,1);

     for v=2:size(hitrate_matris,4)
         total_hitrate_matris(:,:,u) = total_hitrate_matris(:,:,u) + hitrate_matris(:,:,u,v);
     end
 end

Note how we just add the remaining dimensions (from 2 to 5) to total_hitrate_matris(:,:,u) at each iteration of the inner for loop.

[André Svensson]

Oh. I've learned so much today, thank you!