Mean of matrix subarrays without using a loop.

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

Answer 1

[Stephen23]

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

[Santos García Rosado]

Nice and clean code. Thank you Stephen!