st: dealing with duplicate "pairs" of columns

["Vitorino, Maria Ana" <vitorino@wharton.upenn.edu>]

Hi all,
I was wondering if there was a relatively simple way to achieve the following:

My data looks like this:

Person1_id ClosestPerson  Person1_age  
1			2			10	
2			1			20	
3			1			30
4			3			40
...

What I would like to do is to signal "duplicate" rows for which Person1 is the oldest. Since this is hard to explain, the resulting data would be for the example above:

Person1_id ClosestPerson  Person1_age  dup
1			2			10				1
2			1			20				2
3			1			30				0
4			3			40				0
...

Note that the column dup has the following coding:
dup=1 if there is another pair of ppl identical to the one in this row and Person1 is the youngest of the pair
dup=2 if there is another pair of ppl identical to the one in this row and Person1 is the oldest of the pair
dup=0 if there is no other pair of ppl identical to the one in this row

Hope this isn't too confusing...
Suggestions are welcome!

Thanks,
Maria Ana


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