reshape and sum multi-dimensional matrix

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.

Answer 1

[Stephen23]

Where A is your array:

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

Answer 2

[Sammit Jain]

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]

Thanks for your explanation Sammit. Actually, both answers are correct.

Answer 3

[Jan]

Or:

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