# Find unique rows (including rows with reverse x,y) in matrix of x,y coordinates

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Peyman Obeidy le 25 Sep 2018
Commenté : Peyman Obeidy le 25 Sep 2018
I would like to extract unique coordinates for example if x=1, y=2, then this point is similar to y=2,x=1 and only one pair is kept.
x y
1 2
2 1
2 3
3 2
I have tried two approaches; A) using unique comments
[uniqueA M2 M3] = unique(data(:,[1:2]),'rows'); This found no unique row
b) a for loop which I couldn't complete
for j=1:358
clear row3
[row1,col1,v1]=find(data(j,1));
[row2,col2,v2]=find(data(j,2));
[row3,col3,v3]=find(data(:,2)==v1 & Tab_Vn_values2(:,1)==v2);
Tab_Vn_valuesTest(j,:)=Tab_Vn_values2(row3,:);
end
##### 3 commentairesAfficher 1 commentaire plus ancienMasquer 1 commentaire plus ancien
Peyman Obeidy le 25 Sep 2018
I think it is only looking at x1=x2 and y1=y2. Is this right?
Peyman Obeidy le 25 Sep 2018
Thank you KSSV for always being helpful too.

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### Réponse acceptée

Bruno Luong le 25 Sep 2018
Modifié(e) : Bruno Luong le 25 Sep 2018
Try
[~,i] = unique(sort(data(:,1:2),2),'rows')
data(i,:)
##### 3 commentairesAfficher 1 commentaire plus ancienMasquer 1 commentaire plus ancien
Bruno Luong le 25 Sep 2018
Modifié(e) : Bruno Luong le 25 Sep 2018
nothing mysterious
if you want pair (x1,y1) matches the pair (x2,y2) regardless if you swap x and y (in other word after applying any permutation of 2 elements), meaning that if and only if you sort them they matches in order. Sorting a permuted array will bring them back to a unique state.
Peyman Obeidy le 25 Sep 2018
Thank you, great

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