Finding common elements in two matrices of different lengths

Greetings, I’ve a question about comparing matrices 'a' and 'b' then creating a third matrix 'c' based on matching pairs of numbers in two other matrices. Current example:

a = [17,9;23,3;24,3;23,3;24,3;9,6;10,6;23,3;24,3;23,3]

b = [17,1;18,1;21,1;23,3;24,3;23,4;24,4;9,6;10,6;14,12;23,12;24,12;23,14]

My goal is to create 'c' where both columns in 'a' and 'b' are the same. So, row 1 of 'a' would be excluded, as would the first 2 rows of 'b', etc. etc.. Any help with accomplishing this task would be greatly appreciated.

Cheers, Jason

Answer 1

[Walter Roberson]

It is not clear what output you want, considering you have two inputs. Perhaps

c = intersect(a,b,'rows');

or

 c = [ismember(a,b,'rows'); ismember(b,a,'rows')];

[Jason]

Hi Walter,

Thanks for the answers, both of them work (see below). However, intersect turned out to be the more elegant answer. My goal is to create c from the common rows of a and b.

Option #1

c = find(ismember(a,b,'rows'))
d = [];
for i=1:numel(c)
  d(i,:) = a(c(i),:)
end

Option #2

c = intersect(a, b, 'rows', 'stable');

Thanks again for pointing me in the right direction.

Cheers, Jason