MATLAB Answers


How do I get the mean of always 4 columns

Asked by Antonio Melieni on 15 Apr 2019
Latest activity Commented on by Antonio Melieni on 17 Apr 2019
I have a 527040 x 16 double array
I need the row mean of always 4 clomuns
So I need the row mean of column 1:4 5:8 9:12 13:16
So I want the mean([1:4],2) and mean([5:8],2)
but i dont want to wirte it down in that way. I need an more automatic way to do it
any ideas?


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2 Answers

Answer by madhan ravi
on 15 Apr 2019
Edited by madhan ravi
on 15 Apr 2019
 Accepted Answer

AA=permute(reshape(A.',4,1,[]),[2,1,3]); % where A is size 527040 X 16
% if you want to reshape it as matrix then
% reshape(AAA,size(A,1),[]) %% edit removed transpose


The transpose doesnt help.... I get an 4 X 527040 array then....
Matt J
on 15 Apr 2019
Both the permute operation and the transpose operation allocate arrays the same size as A. sepblockfun avoids this.
@Antonio:Matt‘s file exchange is Perfect why not use his solution then?

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Answer by Matt J
on 15 Apr 2019
Edited by Matt J
on 15 Apr 2019

One way is using sepblockfun, downloadable from here
Then you would do,
result = sepblockfun(yourArray, [1,4],'mean');


Thanks, but thats a bit to complicated :)
The only way I can Matt J's one line solution as being "too complicated" is that this is homework. So, you're not allowed to use third-party routines like sepblockfun as is, and it is a tedious matter for you to try to decipher what it is doing and adapt it to your assignment.
Thanks for your function and your help.
Will use your sultion :)

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