MATLAB: Extract submatrix from a large matrix using loop

loop matrix extract small

Dear friends, I have a matrix 1140 by 330. I have to split the matrix into 60 matrices with the size of 19*330 using a for loop. does any one know how to do that?

Best Answer

You can use MAT2TILES ( Download ). For example,

A=rand(1140,330);
C=mat2tiles(A,[19,330]);

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MATLAB: How to save all iteration matrices and put it into big one

You don't have to create splitQ, you can work on Q directly:

 ind = 1:19:size(Q,1); % create the starting indices of the rows
 R = nan(size(R,2), size(R, 2), numel(ind)); % preallocate resulting matrix for speed
 for i = 1:numel(ind)
   R(:,:,i) = corrcoef(Q(ind(i):ind(i)+18,:)); % compute the i'th correlation matrix
 end

You can then access the i'th correlation matrix as

R(:,:,i)

MATLAB: How to use CROSS with 3×1 Matrix on a 3xN Matrix

Unfortunately, the cross( ) function does not auto-expand the dimensions of the operands. So you would have to manually do this or use a loop. E.g., if your vector is v and your matrix is M, then

result = cross(repmat(v,1,size(M,2)),M);

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MATLAB: How to save all iteration matrices and put it into big one

MATLAB: How to use CROSS with 3×1 Matrix on a 3xN Matrix

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