## reshape and sum multi-dimensional matrix

### ehsan (view profile)

on 18 May 2018
Latest activity Edited by Jan

on 28 Jun 2018

### Stephen Cobeldick (view profile)

Hi, I have a 20-by-30-by-40 matrix. I would like to sum each two page of the third dimension. In the end, I need to have a 20-by-30-by-20 matrix.
I appreciate if you could help me.

### Stephen Cobeldick (view profile)

on 18 May 2018
Edited by Stephen Cobeldick

### Stephen Cobeldick (view profile)

on 18 May 2018

A(:,:,1:2:end) + A(:,:,2:2:end)

### Sammit Jain (view profile)

on 18 May 2018

Hi, I think what you're trying to do can be accomplished without reshaping the multi-dimensional matrix.
% Initializing 20x30x40 matrix of random elements
X = rand(20,30,40);
% Splitting the matrix into 2 sets based on the alternating third dimension
% The two sets are of dimensions 20x30x20 each.
% Taking out odd elements of third dimension
setA = X(:,:,1:2:40);
% Taking out even elements of third dimension
setB = X(:,:,2:2:40)
% Adding the two sets A and B
result = setA+setB;
The key here is splitting the main matrix into two 'pages' that you actually want to add.

ehsan

on 18 May 2018

on 28 Jun 2018
Edited by Jan

### Jan (view profile)

on 28 Jun 2018

Or:
squeeze(sum(reshape(A, 20, 30, 2, 20), 3))