How to find the column index of the first nonzero element for every row of a given matrix

Dear all,

I have the following matrix

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

A = 5×4

1 1 1 1 0 1 1 1 0 0 0 1 0 0 1 1 0 1 1 1

and I would like to get an output vector v listing the column indices of the first nonzero element for every row of A:

v=[1;2;4;3;2]

v = 5×1

1 2 4 3 2

How can I do this? Thanks in advance, I appreciate your time and help.

[Torsten]

https://de.mathworks.com/matlabcentral/answers/1664294-how-do-i-find-the-indices-of-nonzero-elements-for-a-matrix-of-logical-vectors?s_tid=srchtitle

Was something wrong with the answers you got here ?

[Distelfink]

Not at all, but this was a different problem I thought. Matt's solution in that thread, to use the find() function, did not work for me in the case here because it yields the column indices of all non-negative values in each row.

Answer 1

[Arif Hoq]

you can find your answer here

https://www.mathworks.com/matlabcentral/answers/365710-how-to-find-first-1-in-every-row

Just follow this:

A=[1 1 1 1; 0 1 1 1; 0 0 0 1; 0 0 1 1; 0 1 1 1];
[~,output]=max(A,[],2)

output = 5×1

1 2 4 3 2

[Distelfink]

Oh, I hadn't found that thread. Thanks a lot, Arif!!