# Replace values ​​in a matrix

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stelios loizidis on 4 Aug 2021
Hello. I have the following problem.
I have a matrix A with dimensions 1X72. I want in matrix B to have the mean per 24 values. That is, matrix B should be 1X3. Next, I want those values ​​in matrix A above 50 to be replaced by the mean. That is, any value in positions A (1:24) above 50 to be replaced by the mean found in B (1), any value in positions A (25:48) exceeding 50 to be replaced by the mean located in B (2) and any value in positions A (49:72) exceeds 50 to be replaced by the mean in B (3).
stelios loizidis on 4 Aug 2021
% A 1X72
B1=A(1:24);
B1_mean=mean(B1);
B2=A(25:48);
B2_mean=mean(B2);
B3=A(49:72);
B3_mean=mean(B3);
B=[B1_mean,B2_mean,B3_mean];
Rik on 4 Aug 2021
Since you seem to be prepared to hard-code the indices: can you think of a way to use my hint to solve your own question?

Matt J on 4 Aug 2021
A=reshape(A,[],3);
B=mean(A,1);
map=A>50;
A=reshape( A.*(~map)+B.*map , 1,[])
stelios loizidis on 4 Aug 2021
It works. Thank you for your help!!!