# st: RE: AW: dealing with duplicate "pairs" of columns

 From "Nick Cox" To Subject st: RE: AW: dealing with duplicate "pairs" of columns Date Wed, 10 Feb 2010 15:03:53 -0000

```See also for related technique

SJ-8-4  dm0043  . Tip 71: The problem of split identity, or how to group
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N.
J. Cox
Q4/08   SJ 8(4):588--591                                 (no
commands)
tip on how to handle dyadic identifiers

Nick
n.j.cox@durham.ac.uk

Martin Weiss

clear*

input byte(Person1_id ClosestPerson  Person1_age)
1			2			10
2			1			20
3			1			30
4			3			40
end

gen lower=min( Person1_id, ClosestPerson)
gen upper=max( Person1_id, ClosestPerson)
bys lower upper ( Person1_age): gen byte dup=!(_N==1)
by lower upper ( Person1_age): replace dup=2 if _n==_N &dup!=0
l, noo

Vitorino, Maria Ana

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

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```