Replace values ​​in a matrix

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).

Your help is invaluable !!!

[KSSV]

What have you attempted?

[stelios loizidis]

I calculated the mean for every 24 values (matrix B). But I have not been able to make the replacement.

[Rik]

If you show your code it is probably easy to modify it to do the replacement.

In the mean time a hint:

a=[1 5 2];
a([false true false])=10
%now a is [1 10 2]

[stelios loizidis]

% 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]

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?

Answer 1

[Matt J]

A=reshape(A,[],3);

B=mean(A,1);

map=A>50;

A=reshape( A.*(~map)+B.*map , 1,[])

[stelios loizidis]

It works. Thank you for your help!!!