Randomly choose one nonzero element in each row of matrix

6 views (last 30 days)
Hello,
I have a 3D-matrix filled with ones and zeros. For example:
ex(:,:,1) =
0 1 0 1
0 0 0 1
1 0 0 1
ex(:,:,2) =
0 1 0 0
1 1 1 1
1 0 0 1
ex(:,:,3) =
0 1 1 0
0 1 1 0
1 0 1 0
In each row I need to randomly select one nonzero element and get its index. Best would be to get a 3 x 1 x 3 matrix with the (column) indexes of the randomly chosen element for each row.
I think I know how to do it with loops, but I want to avoid them since the matrix will be quite big.
Any ideas on how to solve this with no loops?
Thank you in advance for your answers!

Accepted Answer

David Hill
David Hill on 9 Jun 2022
Need a single loop in third dimension.
ex=randi(2,10,17,12)-1;
E=permute(ex,[2,1,3]);
[r,c]=find(E);
N=zeros(size(ex,1),1,size(ex,3));
for k=1:size(ex,3)*size(ex,1)
f=find(c==k);
try%in case some rows don't have any 1's
N(k)=r(f(randperm(length(f),1)));
end
end

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!