MATLAB: Finding similar rows in matrices

comparefindMATLABmatrix manipulation

Hi, i have several matrices that has 3 columns each, but the number of rows is not equal. im trying to find a fast way of comparing the first two columns in all 3 matrices and to find the rows (column 1 and 2) that are identical in all 3 of them. i've tried "ismember", it works ok but when dealing with lots of matrices its too slow.
can anyone recomend a different function? thank you for your help.

Best Answer

I think your best bet for something fast is the intersect() command.
doc intersect
for details. Be sure to use the "rows" argument.
Here is some code that I believe will do what you want, but I have to admit I did not test much:
a=[1,2,3;
1,3,5;
2,5,7];
b=[1,2,6;
1,4,8;
2,5,8];
c=[1,4,7;
1,5,3;
2,5,9];
[ab,ia,ib] = intersect(a(:,1:2),b(:,1:2),'rows')
[abc,iab,ic] = intersect(ab(:,1:2),c(:,1:2),'rows')
a_row_idx = ia(iab)
b_row_idx = ib(iab)
c_row_idx = ic
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