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# st: Data managment- group characteristics

 From Asadullah To statalist@hsphsun2.harvard.edu Subject st: Data managment- group characteristics Date Thu, 21 Aug 2003 07:00:51 -0700 (PDT)

```Hello,

I am having trouble in figuring out how to create some
peer variables for my data. I have a dataset of kids
in households and i need to calculate variables that
reflect the position of a kid (say, aged 6-17) among
other kids (in same age group) in the residential
neighbourhood.

If i wanted to obtain simple peer variables, then the
solution is to calculate the -peer variable- of
interest for each kid (by excluding him/her from the
calculation), following the rule explained in FAQ
section on STATA webpage :
http://stata.com/support/faqs/data/members.html
With little modification of the rule, own siblings can
also be net out from the above calculation of peer
vars.

Problem is in creating variables like, say “relative
birth order” (RBO), for every kid in the sample using
only data on -all other kids in the neighbourhood-
where we need to:  (a) exclude own siblings in
calculation & (b) retain the individual kid (for whom
the variable is being calculated) in calculation.

For kids with no siblings, there is little problem. It
is the presence of own siblings that i am finding
difficult to deal with. IN contrast to common peer
group variables that are constant for kids from same
families, this (within neighbourhood) R/BO may be
different for siblings of different age within a
family. Some form of nested loop (may be as an
extension of the cited FAQ) is necessary, but I
haven’t been able to construct the general form of it.
Once done, I can calculate lots of other  variables
(e.g. what % of kids in the peer group are older in
age, of same age etc. etc.). Any help will be
appreciated. I further elaborate my case below.
Thanks. Asad.

RBO (relative birth order) is calculated as:

g RBO=(BO-1)/(Tot_KIDS-1)

where, "BO" (absolute birth order) is:

egen BO=rank(age*(include)),by(Nid) field

But presence of own siblings mean that both BO and
Tot_KIDS (total no. of other kids in neighborhood) are
incorrect.

For correct Tot_KIDS , we could follow the STATA FAQ
(by Nick) ...

g Tot_KIDS =.
qui sum hid
qui forvalues i = 1 / `r(max)'	{
g include=1 if hid!=`i' & age>=6 & age<18
egen Tot_KIDS_1=sum((age>=6 & age<18)*include),by(Nid)

egen Tot_KIDS _2=sum((age>=6 &
age<18)*include),by(family)
replace Tot_KIDS = Tot_KIDS_1- Tot_KIDS_2 if hid==`i'
drop include Tot_KIDS_*
}

For BO, however, i need a way to exclude own siblings
while executing the following for each kid in the
neighborhood:

egen BO=rank(age),by(Nid) field

Then, I guess, my problem is solved. Following is
sample data where BO is the birth order (within
neighborhood) variable to be calculated for each kid.
“Nid” is neighborhood id, “family” is family id etc.

Nid	family	person	age	BO
1	1	1	40	.
1	1	2	35	.
1	1	3	12	2
1	1	4	6	1
1	1	5	7	1
1	2	1	36	.
1	2	2	31	.
1	2	3	8	3
1	3	1	40	.
1	3	2	12	4
1	3	3	12	4
1	3	4	8	3

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