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How to reshape matrix without loop?

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John on 26 Jul 2017
Edited: John on 26 Jul 2017
Want to rearrange the matrix A(a,b,c,d) to B(b,c1,c2,d,a), where a,b,c,d are dimensions, c=c1*c2. If known c1=3, for example, B should be:
for nc=1:c1
Can it be done more elegantly and without the loop?

Answers (1)

John D'Errico
John D'Errico on 26 Jul 2017
WTP? Effectively two lines, one more to get the size of A if you don't know it already.
[a,b,c,d] = size(A);
B = reshape(A,[a,b,c1,c/c1,d]);
B = permute(B,[2 3 4 5 1]);
There is no need to use fix, because if c is not exactly divisible by c1, then A won't have the correct number of elements for a reshape anyway.
  1 Comment
John on 26 Jul 2017
Edited: John on 26 Jul 2017
Hi, John: Will this make the dimension c1 to be the index (1,4,7,10...),(2,5,8,11...), (3,6,9,12...) from c respectively? Thanks.

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