how to compare to a row in matlab

I have a matrix similar to this one:

1468    1468

1468    1711

1468    1469

1711    1468

1711    1711

1711    1469

1469    1468

1469    1711

1469    1469

and I would like to remove the entry (i,j) iff开发者_如何学编程 the entry (j,i) exists. For example, I would like to remove 1711 1468 as 1468 1711 appears above it.

How do I do this?

Assuming that the order doesn't matter for removing rows, you can combine SORT and UNIQUE like this:

m = [1468    1468
1468    1711
1468    1469
1711    1468
1711    1711
1711    1469
1469    1468
1469    1711
1469    1469]

[~,v]=unique(sort(m,2),'rows');

trimmedM = m(sort(v),:) %# keep the row ordering as in the original

trimmedM =
        1468        1468
        1711        1468
        1711        1711
        1469        1468
        1469        1711
        1469        1469

Note that unique will retain the last of the duplicate entries, which seems to fit with your requirements.

I assume by the nature of the problem that order is irrelevant. Then you could just store the smaller number in the first column and look for duplicate rows. This question has some suggestions for that. This line will perform that sort so the referenced methods will work:

x = [min(x(:,1),x(:,2)),max(x(:,1),x(:,2))]