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Re: st: genealogy: how to calculate sibship size

From   n j cox <>
Subject   Re: st: genealogy: how to calculate sibship size
Date   Thu, 07 Sep 2006 10:54:26 +0100

Ronnie Babigumira already directed you to an FAQ explaining various tricks. It may be more complicated than you need.

I just wanted to add that if each observation is a person and your variables are as stated then the number of people sharing each pair of parents is given directly by

bysort ??ther_id : gen n = _N

Thus suppose that our data are

donor_id father_id mother_id
1 A Z
2 A Z
3 A Y
4 A Y
5 B Y
6 C X

then after this

bysort ??ther_id : gen n = _N

you have

donor_id father_id mother_id
1 A Z 2
2 A Z 2
3 A Y 2
4 A Y 2
5 B Y 1
6 C X 1

Note that you don't need a combined id, as you can just
use the two parent ids jointly.

(I enjoyed using the wildcard ??ther_id, as this will catch

father_id mother_id

and (almost certainly) nothing else in your data. If you are
really using French then fortuitously (and fortunately)


works the same way.)


BAIJER Jan 212040, Ph.D.

I'm trying to have Stata calculate the number of sibs for each of the
families in a list that is composed as follows :


From this, I can calculate a unique identifier for the parent couple, by
concatenation of father_id and mother_id.

But, I have no idea how to proceed for this one ...

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