How to arrange one row vector into a row x column matrix?

Question

Miroslav Josic 2017-2-7

0
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https://ww2.mathworks.cn/matlabcentral/answers/323778-how-to-arrange-one-row-vector-into-a-row-x-column-matrix

评论： Miroslav Josic 2017-2-7

Hi guys, I would appreciate your help on this problem. I have a row vector (M) of size 1x2108 which contains data for 62 countries and 34 industries for each country. So, column 1:34 is industry data for country 1, 35:68 country #2 etc. I just need to make a matrix which will be of a size 62x2108 and have data in following way: - row #1, columns 1:34 for country #1, elsewhere zeros - row #2, columns 35:68 for country #2, elsewhere zeros - row #3, columns 39:102 for country #3, elsewhere zeros etc.

So far, I used this code:

M_new=zeros(62,2108);
for i=1:62
    for j=1:62
        M_new(i,((j-1)*34+1):(j*34))=M(1,((j-1)*34+1):(j*34));
    end
end

but I only get row vector copied 62 times in each row.

Best,

Miroslav

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Answer 1

Guillaume 2017-2-7

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https://ww2.mathworks.cn/matlabcentral/answers/323778-how-to-arrange-one-row-vector-into-a-row-x-column-matrix#answer_253719

在 MATLAB Online 中打开

M_new = [reshape(M, 34, 62); zeros(2108, 62)];
M_new = reshape(M_new(1:end-2108), 2108, [])'

No need for a loop.

However, I question the wisdom of using 62 times more memory to store the same information.

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Miroslav Josic 2017-2-7

Hi Guillaume,

Thanks a lot for your quick reply, indeed it works perfectly. I was using loop for some other re-arrangements and it did not take much time so I tried to use it here again.

Best,

Miroslav

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