Reverse of find groups

I have used findgroups to convert 2 column data to single column unique values. Like 1,1 was converted to 1. 1,2 to 2. 2,1 to 3. 2,2 to 4 and so on. I now want to reverse this operation, i.e., given integer from 1 to 48, I would like to get back the two column values.

Answer 1

[Jan]

Use the 2nd output of findgroups:

A = [1,1; 1,2; 2,2; 3,3; 3,4; 1,3; 1,2];
[G, ID1, ID2] = findgroups(A(:, 1), A(:, 2));
AG = [ID1, ID2];

Now the i.th row of AG contains the 2 column values of the i.th group of G.

AG(3, :)

ans = 1×2

1 3

I assume unique('rows') is more efficient here.