How to select the combinations without repetitions in a matrix?

Hi Everybody,

I have a question regarding matrix sorting. I have a matrix "A" a 6 by 2 matrix.

A=[

    1  2
    3  2
    1  2
    2  1
    1  4
    2  5];

As you can see row 1,3 and 4 have the same answer but inter changed numbers. How do we get matrix "B" without any combination repeats. Thank you

[Image Analyst]

In B, would you want to take row 3 or row 4 from A?

[Adam Silva]

Since row 1 is matching the combinations in row 3 and 4 I want to take both row 3 and 4 off. So row 1 will be in B not row 3 and 4.

Thanks

[Image Analyst]

Azzi's code should do it then, since you want to take the first occurrence , regardless of the order of the columns. WARNING: If you have floating point numbers and not integers, be aware of the FAQ: http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Adam Silva]

Hi, I only have integers. But Azzi'z code gave me an error,

??? Error using ==> unique at 33 Unrecognized option.

Error in ==> nodesort at 209 [ii,jj]=unique(sort(A,2),'rows','stable')

Answer 1

[Azzi Abdelmalek]

[ii,jj]=unique(sort(A,2),'rows','stable')
B=A(jj,:)

[Adam Silva]

Hi Azzi,

My actual A is 204 by 2 matrix. When I ran your code it gave me the following error.

??? Error using ==> unique at 33 Unrecognized option.

Error in ==> nodesort at 210 [ii,jj]=unique(sort(A,2),'rows','stable');

[Azzi Abdelmalek]

Then use

[ii,jj]=unique(sort(A,2),'rows')
B=A(jj,:)

[Azzi Abdelmalek]

Shape commented

Ok got it. I removed the option 'stable'.

Thank you