MATLAB: Sum subarrays of a Matrix.

Question

Hi Mathworks community! Could someone give me a hand?

I'm having trouble trying to sum parts of the arrays of a matrix. Let's say I have the following matrix A of r rows and c columns (rxc).

A = [1,2,3,4,5,6,7,8,9; 10,11,12,13,14,15,16,17,18; 19,20,21,22,23,24,25,26,27]

And what I would like to to is to divide each array in n subarrays (n=3) and sum each of those subarrays. In this case, it would be the sum of every three positions. Getting an output suchs as:

out = [5,15,24; 33,42,51; 60,69,78]

Thank's for the help!

Santos

Answer 1

One-liner

transpose(reshape(sum(reshape(A',3,[])),3,[]))

Or

transpose(cell2mat(cellfun(@sum,mat2cell(A',[3,3,3],3),'unif',0)))