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Getting indices of all unique rows

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Andrew
Andrew on 3 Dec 2012
I have a matrix "M" with 1,000 rows and 5 columns. The first column is the row number and columns 2:5 are ordinal numbers (-1, 0, 1). To get the number of unique rows with respect to columns 2:5 I've used the following:
uM = unique(M(:, 2:5));
But what I really want is the row indices for each unique row.
Let's say that M is really:
[1 0 1 1 -1; 2 1 0 -1 -1; 3 0 1 1 -1; 4 -1 0 -1 1 ]
I'd like to obtain a cell array vector that has:
{ (1, 3), 2, 4 }
Any ideas?
Thanks!

Accepted Answer

per isakson
per isakson on 3 Dec 2012
Read the documentation on unique and note that there is a second and third output argument. Doc says:
[C,ia,ic] = unique(A,'rows')

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