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Mean of matrix subarrays without using a loop.

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Santos García Rosado
Santos García Rosado le 16 Mar 2021
Hi Mathworks community.
I'm trying to calculate the mean value of my matrix subarrays without taking the zero values into account. I know how to do it using a loop, but in this case I'd like to avoid it.
The code should take matrix A:
A = [1 0 3 5 0 7; 0 2 6 0 8 0; 3 5 0 0 2 0]
And calculate the mean value of the subarray for each row in steps of 3. So the output should look like:
Out = [2 6; 4 8; 4 2]
I'm trying to improve this code, since I'll be working with much bigger matrixes and I won't be able to do it manually:
Out = mean(nonzeros(A(1,1:3)));
Any help would be much appreciated.
Thanks in advance,
Santos

Réponse acceptée

Stephen23
Stephen23 le 16 Mar 2021
Modifié(e) : Stephen23 le 16 Mar 2021
A = [1 0 3 5 0 7; 0 2 6 0 8 0; 3 5 0 0 2 0]
A = 3×6
1 0 3 5 0 7 0 2 6 0 8 0 3 5 0 0 2 0
B = reshape(A.',3,[]);
B(B==0) = NaN;
C = reshape(mean(B,1,'omitnan'),[],size(A,1)).'
C = 3×2
2 6 4 8 4 2
Or
F = @(s)mean(nonzeros(s.data));
C = blockproc(A,[1,3],F) % requires the Image Toolbox.
C = 3×2
2 6 4 8 4 2
  1 commentaire
Santos García Rosado
Santos García Rosado le 16 Mar 2021
Nice and clean code. Thank you Stephen!

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