# Averaging specific rows and specific columns in N by N matrix

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Abdulhakim Alezzi on 9 Jan 2023
Commented: Mathieu NOE on 11 Jan 2023
hI friends,
I am trying to do averging for specfic rows with specific columns in C=19*19 matrix to have a final matrix of 5*5.
I am using the following code :
Y=mean (C([3:5 10:11 16:17, 12:13 19, 1 7, 2 6 8, 14:15],[3:5 10:11 16:17, 12:13 19, 1 7, 2 6 8, 14:15]));
But the output matrix is 1*17.
Any help will be appreciated.

Mathieu NOE on 10 Jan 2023
hello
you need somehow to split your 5 domains into separate arrays (like a cell array as below)
then you can perform a for loop on each submatrix
try this
C = rand(19,19);
ind = [{[3:5 10:11 16:17]}; {[12:13 19]}; {[1 7]}; {[2 6 8]}; {14:15}];
for ci = 1:numel(ind) % row
for cj = 1:numel(ind) % col
ind_r = ind{ci};
ind_c = ind{cj};
Y(ci,cj)=mean(C(ind_r,ind_c),'all');
end
end
##### 2 CommentsShowHide 1 older comment
Mathieu NOE on 11 Jan 2023
My pleasure !

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