Reordering columns in a matrix
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Hello,
I want to multiply 2 matrices elemntwise and swap columns 1 and 2 in the result:
A = [1 2 3; 1 2 3; 1 2 3; 1 2 3];
B = -1*ones(size(A));
AB = A.*B;
C = AB(:,[2 1 3]);
I am using 2 steps to do this (lines 3 & 4). How do I do this in a single step (single line of code)?
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Answers (5)
the cyclist
on 30 Dec 2011
You cannot index results in that way. See, for example, the accepted answer in this thread about features that are "missing" in MATLAB:
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Fangjun Jiang
on 30 Dec 2011
If you have to do this, you can use subsref()
a=magic(3)
b=subsref(a,substruct('()', {':',[2,1,3]}))
In your case, it will be
C = subsref(A.*B, substruct('()', {':',[2,1,3]}))
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Andrei Bobrov
on 30 Dec 2011
circshift(fliplr(A.*B),[0 -1])
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Fangjun Jiang
on 31 Dec 2011
What a surprise answer, andrei! But I would still go with the subsref() function. After all, it is the function format of the re-arrangement. To challenge you, what if A.*B is a 4x4 or 5x5 matrix but I want to swap the first and second column?
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