Delete duplicated row in a matrix

I have two matrix like this:

    a=[1 2 3; 2 1 3; 2 2 4;2 3 6;2 4 5;3 7 7;3 6 6]
    b=[1 2 5;2 2 5;2 3 6;2 4 7;3 6 7]

I want delete, without change order, the duplicated rows without consider third column, but only respect column 1 and 2.

So the output would be: [2 1 3; 3 7 7]

Answer 1

[Tom]

   I = ~ismember(a(:,1:2),b(:,1:2),'rows');

   a = a(I,:)