# How to repeat rows of matrix?

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Tom on 13 Jun 2013
Hi,
I have a matrix and a vector indicating how many times the corresponding lines in the matrix should appear. I'd like to turn this into a single matrix.
For example:
M= 1 2 V=1
2 3 2
4 3 1
2 4 2
should become
M =1 2
2 3
2 3
4 3
2 4
2 4
Does anyone have advice on how to accomplish this? Many thanks.

Matt Kindig on 13 Jun 2013
Edited: Matt Kindig on 13 Jun 2013
One way:
f = @(k) repmat(M(k,:), round(V(k)), 1);
MM = cell2mat(arrayfun(f, (1:length(V))', 'UniformOutput', false));

Roger Stafford on 13 Jun 2013
Here's yet another possibility:
p = accumarray(cumsum([1;v]),1);
M = M(cumsum(p(1:end-1)),:);

Matt J on 13 Jun 2013
Edited: Matt J on 13 Jun 2013
c=cumsum(V);
[~,i]=max(bsxfun(@le,1:c(end),c));
MM=M(i,:),

Azzi Abdelmalek on 13 Jun 2013
out=cell2mat(arrayfun(@(x) repmat(M(x,:),V(x),1),[1:numel(V)]','un',0))

Matt J on 13 Jun 2013
Edited: Matt J on 13 Jun 2013
c=cumsum(V);
z=sparse(1,c(end)+1-c,1,1, c(end));
m=fliplr(cumsum(z))
Mnew = M(m(1)+1-m,:),