# Find unique in matrix of x,y coordinates

33 views (last 30 days)
Ruchi Bhatia on 19 Dec 2017
Commented: Ruchi Bhatia on 20 Dec 2017
Hello, I would love your help.
If I have a matrix of x,y coordinates for example:
x y
A=[ 2.5 3.5
1.2 3.5
2.2 1.2
1.2 3.5
4.0 2.2 ]
How do I find a unique of this? In the above example one instance of x,y (1.2, 3.5) will be removed?

Kelly Kearney on 19 Dec 2017
To find unique rows, you can use unique with the 'rows' option. (The 'stable' option preserves the input order, if that's important for your application).
unique(A, 'rows', 'stable')
Ruchi Bhatia on 19 Dec 2017
Thanks. Wow, didn't realize it was that straight forward.

### More Answers (2)

Image Analyst on 19 Dec 2017
Try unique() with the 'rows' option:
uniqueRowsOfA = unique(A, 'rows')
Ruchi Bhatia on 20 Dec 2017
thank you

Kaushik Lakshminarasimhan on 19 Dec 2017
Did you try this?
[C,IA] = unique(A,'rows');
C contains all unique rows of A. IA contains the indices of the rows of A that are in C. So if you want the indices of the rows that were removed, you can use:
[nrows,~] = size(A);
notIA = setdiff(1:nrows,IA); % duplicate rows
Ruchi Bhatia on 19 Dec 2017
Thank you! Very helpful.

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