Removing columns from a matrix

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Atreyu91
Atreyu91 on 22 Aug 2015
Commented: Star Strider on 23 Aug 2015
Can anyone please how me how to remove columns from a matrix?
an example of what I am trying to do is remove the 4 columns of this 2x6 matrix:
[a,0,0,0,0,b; c,0,0,0,0,d]
to
[a,b;c,d]

Accepted Answer

Star Strider
Star Strider on 22 Aug 2015
One possibility:
[a,b,c,d] = deal(3,5,7,13); % Populate Variables
M = [a,0,0,0,0,b; c,0,0,0,0,d];
Mresult = reshape(M(M~=0), size(M,1), [])
Mresult =
3 5
7 13
  3 Comments
Atreyu91
Atreyu91 on 23 Aug 2015
Do you know how to reverse this process and add the zeros back into the matrix?
Star Strider
Star Strider on 23 Aug 2015
My pleasure!
You have to know the number of zeros you want to add. That information was lost in the first step. Probably the easiest way to do it though would be something like this:
Mreverse = zeros(2,6);
Ix = sub2ind(size(Mreverse), [1 1 2 2], [1 6 1 6]);
Mreverse(Ix) = [a b c d];
There are probably a number of ways to do it, this is one.

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