Find column position of trues in a binary matrix

Question

Alex Ferrer 2020-3-19

评论： Alex Ferrer 2020-3-20

Hello,

I have a binary matrix with with a large number of rows (~10^6) and small number of colums (~10) where the number of trues in each row is fixed.

I would like to obtain a matrix that for each row I have the column position of the trues.

For example:

I have the following binary matrix

A = [1 0 1 0 0;...
     0 0 1 0 1;
     ...
     ...
     1 1 0 0 0];

and I would like to obtain

 c = [1 3;...
      3 5;...
      ...
      ...
      1 2];

Answer 1

Fangjun Jiang 2020-3-19

编辑：Fangjun Jiang 2020-3-19

see if you can get it from [i,j]=find(A)

>> A = [1 0 1 0 0;
    0 0 1 0 1;
    1 1 0 0 0];
[R,~]=find(A.');
out=transpose(reshape(R,2,[]))
out =
     1     3
     3     5
     1     2

Alex Ferrer 2020-3-20

Thanks, very efficient!