# Sum subarrays of a Matrix.

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Santos García Rosado 2021 年 2 月 25 日

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

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### 採用された回答

Fangjun Jiang 2021 年 2 月 25 日

One-liner
transpose(reshape(sum(reshape(A',3,[])),3,[]))
Or
transpose(cell2mat(cellfun(@sum,mat2cell(A',[3,3,3],3),'unif',0)))
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Santos García Rosado 2021 年 2 月 26 日
I'm using this code for Simulink and the first answer your proposea works perfectly fine. However, Simulink seems not to like the function cell2mat you wrote on the second line but it does work okay with Matlab. Thank's for the help Fangjun!

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### その他の回答 (1 件)

Matt J 2021 年 2 月 25 日

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Santos García Rosado 2021 年 2 月 26 日
Nice function! I'm saving it for the future! Thanks Matt!

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R2020b

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