extract matrix from for loop

Question

0 个投票

Hi,

I want to extract a 2x2 matrix from each iteration of a for loop. Normally I would use something like

for loop=1:1:10
m=[a b c d];
m2(loop)=m;
end

but this doesn't work because of the increased dimensions. Can anyone help?

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Answer 1

Matt Fig 2011-5-16

1 个投票

Use cell arrays, or stack along the third dimension.

for loop=1:1:10
   m=[a b c d]; % I assume this is only a place-holder for code.
   m2{loop}=m;  % Notice the curly braces, not parenthesis.
end

Or,

for loop=1:1:10
   m=[a b c d]; % I assume this is only a place-holder for code.
   m2(:,:loop)=m;  % A 3D array.  Each page is a matrix
end

Also note, that if your final array m2 will be much larger than this you will definitely want to pre-allocate the space.

Answer 2

Sean de Wolski 2011-5-16

0 个投票

m2 = repmat(m,[1 10]);

or

m2 = repmat(m,[10 1]);