Dear Statalist,
I have a large vital statistics register of all births in Denmark and
have the following variables:
Offspring ID ('offid')
Birth order ('bo')
Maternal ID ('mothid')
If the birth order number is duplicated within a sibling set, multiple
births are indicated. Eg. for 3 mothers (101,102,103):
mothid bo offid
101 1 1
101 2 2
102 1 3
102 1 4
103 1 5
103 1 6
103 1 7
Mother 101 has two singleton offspring (1,2), mother 102 has twins
(offspring 3,4) and mother 103 has triplets (offspring 5-7).
I'd like to add a multiplicity indicator ('multi') to the data set, i.e.:
mothid bo offid multi
101 1 1 1
101 2 2 1
102 1 3 2
102 1 4 2
103 1 5 3
103 1 6 3
103 1 7 3
I've looked at the 'egen' command but can't see anything suitable.
Does anyone have any ideas as to how I can write a Stata
command to generate this variable?
Many thanks in advance,
Roger Webb
University of Manchester (UK)
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