How to insert rows into a matrix

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Elaheh 2018-12-14

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评论： Mohsin Shah 2019-4-15

Hi

I have a matrix (748*6). I need to insert one row after every 3rd row. How should I do that? the resulting martix should be (1126 *6).

Thank you

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Jan 2018-12-14

编辑：Jan 2018-12-14

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This cannot work. "After every 3rd row" means, that the number of rows would grow by 4/3. Example with 6 elements:

[1,2,3,<insert>, 4,5,6,<insert>]

Maybe you mean "after every 2nd row" or "in every 3rd row". Then the number of rows grows by a factor of 3/2. This is near to the given sizes, but not exactly: 748 / 2 * 2 is 1122, not 1126.

Please post a short example with inputs and outputs to clarify, what you want.

You did not mention what you want to insert: zeros, NaNs, values from another matrix? "Inserting rows" is not clear in this point.

Elaheh 2018-12-14

apologize for not being clear. This is one part of data. Current table is on the right and the one I need to create is on the left.

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Answer 1

Jan 2018-12-14

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If the details with the size of the output are cleared, something like this will solve the problem:

A = rand(748, 6);  % Test data
n          = 3;  % In each 3rd row
m          = true(748 / (n-1) * n, 1);
m(n:n:end) = false;
B          = zeros(numel(m), 6);
B(m, :)    = A;