Manipulate multidimensional matrix in for loop

Question

Anna 2017-5-3

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https://ww2.mathworks.cn/matlabcentral/answers/338502-manipulate-multidimensional-matrix-in-for-loop

评论： Andrei Bobrov 2017-5-3

Hi, I have a matrix called multidim with 2x100x3 values. I would like to make this a 6x100 matrix by adding the matrix defined in each page under the previous one.

for i = 1:2
matrix = [multidim(:,:,i);multidim(:,:,i+1)];
end

This is what I have tried, but this only works if I have a 2x100x2 matrix. How do I make this a loop which remembers the previous created matrix and uses this in order to keep adding rows from the next page?

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Answer 1

Andrei Bobrov 2017-5-3

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a = num2cell(multidim,[1,2]);
matrix = cat(1,a{:});

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Anna 2017-5-3

This works! Thank you so much!

Stephen23 2017-5-3

编辑：Stephen23 2017-5-3

在 MATLAB Online 中打开

Note my answer is just one line, does not waste memory with unnecessary variables in the workspace, and runs around twice as fast as this answer:

Elapsed time is 6.32136 seconds. % this answer
Elapsed time is 3.98123 seconds. % my answer

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Answer 2

Stephen23 2017-5-3

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https://ww2.mathworks.cn/matlabcentral/answers/338502-manipulate-multidimensional-matrix-in-for-loop#answer_265465

编辑：Stephen23 2017-5-3

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Use permute and reshape:

>> X(:,:,1) = [0,1,2;3,4,5];
>> X(:,:,2) = [6,7,8;9,10,11];
>> reshape(permute(X,[1,3,2]),[],3)
ans =
    0    1    2
    3    4    5
    6    7    8
    9   10   11