MATLAB: Finding last non-zero rows for individual columns of a matrix without loops

Question

I have the following code:

A =[1     2     3;
     1     0     1;
     0     5     1;
     1     0     2;
     2     3     2];
 
 [row,~] = find(A(1:4,[1,2]),1,'last');

What I was hoping to achieve through the above code is to find the last non-zero rows for individual columns. So my expected answer was

 row = [4 3] % since for the first column, the first non-zero element is on 4th row and similarly on 3rd row for the second column

However, with the above code, the answer I am getting is

 row = 3

I have done it with a for loop, but with the size of data I have, it is computationally expensive to do loops. I was hoping to get it done without loops.

Thank you in advance for your kind contribution.

Answer 1

Try this

[r,c] = find( A==0 );
[~,ixa] = unique( c, 'last' );
>> r(ixa)
ans =
     3
     4