Delete unique element in column

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Mate 2u
Mate 2u el 29 de Jun. de 2012
Editada: Miguel L el 27 de Dic. de 2015
Hi I have a 25,000,000x2 matrix. I want to delete all Rows which have the same elements in column 1. So I would require only unique elements in column 1 and their corresponding values in column 2.
  3 comentarios
Jan
Jan el 29 de Jun. de 2012
Editada: Jan el 29 de Jun. de 2012
Mate 2u has written as comment to my wrong answer:
Hi Jan for [1,2; 1,3; 3,4] we would expect to see => [1,3; 3,4] as 1 occured more than once (take the last of the non unique values).
This means, that he does not "want to delete all Rows which have the same elements in column 1".
Miguel L
Miguel L el 27 de Dic. de 2015
Editada: Miguel L el 27 de Dic. de 2015
¡Hello Jan!
Regarding to this question, actually I wanna get "a = [1,2; 1,3; 3,4] => [3,4] ", as you suggest at first ¿Could you help me? Tank you in advance.

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Jan
Jan el 29 de Jun. de 2012
What about:
unique(x, 'rows')
?
  1 comentario
Ryan
Ryan el 29 de Jun. de 2012
A = [1 2; 1 3; 3 4];
unique(A,'rows')
ans =
1 2
1 3
2 4

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Ryan
Ryan el 29 de Jun. de 2012
Editada: Ryan el 29 de Jun. de 2012
Based off of Jan's answer:
A = [1 2; 1 3; 3 4];
[B, I, J] = unique(A(:,1),'last');
NewMatrix = A(I,:);

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