# How to duplicate rows of a matrix if the number of copies for each row are different?

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Hung Dao on 9 Nov 2021
Commented: Hung Dao on 9 Nov 2021
Hi all,
I want to duplicate each rows of a matrix according to the numbers given in a vector.
For example, I have matrix A and vector , I want to duplicate the first row of A 2 times, second row by 4 times and third row by 5 times.
Is there any way to do this?
Thank you for your help.

Stephen on 9 Nov 2021
Edited: Stephen on 9 Nov 2021
out = repelem(A,b,1)
Hung Dao on 9 Nov 2021
Thank you very much. This is exactly what I need.

### More Answers (2)

KSSV on 9 Nov 2021
b = [2 4 5] ;
A = repmat(b,2,1)
A = 2×3
2 4 5 2 4 5
B = repmat(b,3,1)
B = 3×3
2 4 5 2 4 5 2 4 5
##### 1 CommentShowHide None
Hung Dao on 9 Nov 2021
Thanks for your answer but that is not really what I am asking for.

Sulaymon Eshkabilov on 9 Nov 2021
It can be done in a few different ways, e.g.:
A = magic(3)
A = 3×3
8 1 6 3 5 7 4 9 2
b = [2, 4, 5];
AA = [repmat(A(1,:), b(1),1);repmat(A(2,:), b(2),1); repmat(A(3,:), b(3),1)]
AA = 11×3
8 1 6 8 1 6 3 5 7 3 5 7 3 5 7 3 5 7 4 9 2 4 9 2 4 9 2 4 9 2
% Alternative way:
A = magic(3);
b = [2, 4, 5];
AA =[];
for ii = 1:numel(b)
AA = [AA; repmat(A(ii,:), b(ii),1)];
end
AA
AA = 11×3
8 1 6 8 1 6 3 5 7 3 5 7 3 5 7 3 5 7 4 9 2 4 9 2 4 9 2 4 9 2
##### 2 CommentsShowHide 1 older comment
Sulaymon Eshkabilov on 9 Nov 2021
I don't believe there is an alternative more efficient way than using [for .. end] or [while .. end] loop.

R2018a

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