Extract sub-matrices from a big matrix

Question

androidguy 2017-3-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/332634-extract-sub-matrices-from-a-big-matrix

评论： androidguy 2017-3-29

I have an example matrix like the one given below. Original size of my matrix is (83193 x 2). I want extract every 2 rows and make a 2 x 2 matrix from this big matrix. For example:

Changed into:

A = [1 2; 3 4]
B = [5 6; 7 8]
C = [9 10; 11 12]

How can I do this operation?

Thanks!

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Answer 1

Jan 2017-3-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/332634-extract-sub-matrices-from-a-big-matrix#answer_260930

在 MATLAB Online 中打开

X  = rand(83193, 2);
s1 = size(X, 1);
XX = X(1:s1 - rem(s1, 2), :);  % Number of blocks needs to be multiple of 2
Y  = permute(reshape(XX, 2, [], 2), [1, 3, 2]);

Now Y(:, :, i) is the i.th 2x2 matrix. This is much more efficient than creating 41596 variables.