How to repeat rows of matrix?

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.

Answer 1

[Matt Kindig]

One way:

f = @(k) repmat(M(k,:), round(V(k)), 1);
MM = cell2mat(arrayfun(f, (1:length(V))', 'UniformOutput', false));

Answer 2

[Roger Stafford]

Here's yet another possibility:

 p = accumarray(cumsum([1;v]),1);
 M = M(cumsum(p(1:end-1)),:);

Answer 3

[Matt J]

   c=cumsum(V);
   [~,i]=max(bsxfun(@le,1:c(end),c));

   MM=M(i,:),

Answer 4

[Azzi Abdelmalek]

out=cell2mat(arrayfun(@(x) repmat(M(x,:),V(x),1),[1:numel(V)]','un',0))

Answer 5

[Matt J]

 c=cumsum(V); 
 z=sparse(1,c(end)+1-c,1,1, c(end)); 
 m=fliplr(cumsum(z))

 Mnew = M(m(1)+1-m,:),