How to find set of 3 in a 122x4 matrix?

I have a matrix that is 122x4. These have index numbers 1-36 with two only rows containing three points that are common between them. How can I find these pairs?

ex

A=[ 1 2 13 15;
    1 2 15 35;
    1 2 17 22;
    1 2 22 36...]

(there is not a pattern throughout the matrix like there are in the first couple rows) I want some thing that can identify the pair of combos

combos = [1 2;
          3 4]

where 1,2,3,and 4 are row numbers

If I can also print out the numbers they share that would be great too combos = [1 2 1 2 15;...etc

[dpb]

"...three points that are common" for what working definition of "common"? Same three values in same locations or simply the three values in the row as in another, ...?

Also, at least give a set of data that contains matche(s) that meet the criteria for somebody to work with...

[Image Analyst]

Indexes should go from 1 to 122 for the first index, which is rows, and from 1 to 4 for the second index which is columns. How do you get 1 to 36 for the indexes? Did you mean values instead of indexes?

What does "two only rows" mean? Do you mean "only two rows"?

Have you tried a simple brute force approach of simply looping over all locations doing the checking?

[John Hunt]

Thank you for adjusting my question so it was easier to read. @dpb - I just need to find the three values in one row then find those three numbers in a different row. The data set that included in the question are the first four rows of my data. So in the first row there is a 1, 2, and 15. Then in the next row there is the same numbers. I just want to find which rows have the same three numbers for a set of numbers (like 1,2,15) - @Image Analyst - yes sorry values of 1 to 36. There should only be two rows that share the same three values. I have tried to loop through, however I am very new to matlab and my loop failed.

[dpb]

Well, yes, but... :) Are the three numbers as shown in the first three positions or three numbers matching out of the four in the record as Guillame presumes?

[John Hunt]

yeah that is what I am trying to get over, I am not using intersect like he does.

[dpb]

Say what!!!??? I have no klew what the above is intending to say.

Are the three values you're trying to match those in the first three columns only or is it three out of the four in the line that are to be found?

[John Hunt]

three out of the four need to match three out of four for the other rows

Answer 1

[Guillaume]

This is O(n^2) so is going to be slow for largish matrices. I haven't got the time to think of a cleverer algorithm:

pairs = zeros(0, 5);
for row1 = 1 : size(A, 1)
   for row2 = row1+1 : size(A, 1)
      commonnumbers = intersect(A(row1, :), A(row2, :));
      if numel(commonnumbers ) == 3
         pairs = [pairs; row1, row2, commonnumbers]; %#ok<AGROW>
         break;  %assumes that there is always only one other row that matches
      end
   end
end

[John Hunt]

Thank you I will go through it to see if I can get it to do what I need