How can I tell if a rectangular matrix has duplicate rows in MATLAB?

Question

I have an n-by-m rectangular matrix (n != m). What\'s the best way to find out if there are any duplicate rows in it in MATLAB? What\'s the best way to find the indices of t

Answer 1

You can use the functions UNIQUE and SETDIFF to accomplish this:

>> mat = [1 2 3; 4 5 6; 7 8 9; 7 8 9; 1 2 3];    %# Sample matrix
>> [newmat,index] = unique(mat,'rows','first');  %# Finds indices of unique rows
>> repeatedIndex = setdiff(1:size(mat,1),index)  %# Finds indices of repeats

repeatedIndex =

     4     5