MATLAB: How can I create cumulative matrix.

Question

Hello a question please.

I have matrix P with size (452*500). I want to select random selection with roulette wheel selection. I write something:

   r=rand;
   c=reshape(p,1,[]);
   c1=cumsum(c);
   j=find(r<=c1,1,'first');
   [j1 j2]=ind2sub(size(p),j);
end

but I want to remove part " c=reshape(p,1,[]);" and create cumulative matrix of p directly without reshaping it to matrix c. How can I do it?

Thank you.

Answer 1

Something like this? :

r = rand;
jj = find(r<=cumsum(p(:)),1,'first');
[j1,j2] = ind2sub(size(p),jj);

Note I also renamed your variable j, which is also one of names of the inbuilt imaginary unit .