how to look for repetions in a matrix with condition on the last column

I have a matrix A like this:

[0 1 0 2 1 ;
0 1 1 2 0 ;
0 0 1 2 1 ]

I would like to obtain a vector filled with the column position where there is a same number for a certain condition on the last column...in other words: look in the A(1:4, columns where A(:,5)==1) which correspond to

A(1,1:4) = [0 1 0 2] and
A(3,1:4) = [0 0 1 2]

and find the position where there is the same number; save in a vector 1 and 4. thanks!

Answer 1

[KL]

You just need to use indexing with find to get the indices of the rows that fullfil your condition,

A = [0 1 0 2 1 ;
0 1 1 2 0 ;
0 0 1 2 1 ];
ind = find(A(:,end)==1);
res = A(ind,1:end-1)

here ind has the row numbers of the matrix A that satisfy your condition and res extract the needed elements from the respective rows.

ind =
     1
     3
res =
     0     1     0     2
     0     0     1     2

[Stephen23]

didi'a "Answer" moved here:

Thanks a lot! But i need to search also for the repetion in the res matrix....and create a vector with the column indexes where the repetions happen...in this case vector with only one elemnt,1, because only in column 1 i have a repetion of 0.