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You can -generate- a dummy for "being a substitute". What do you want to happen for adjacent sampled schools? Their substitutes must overlap, such as 324 and 325 in my example:
*******
vers 11
clear*
set obs 4000
set seed 43532
gen int school=_n
gen randomnumber=runiform()
sort randomnumber
gen sampled=_n<=300
sort school
gen byte substitute=sampled[_n+1] | sampled[_n-1]
//problem: sometimes sampled schools adjacent to each other
cou if substitute
l in 322/326
*******
HTH
Martin
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Gáti Annamária
Sent: Mittwoch, 6. Januar 2010 12:56
To: [email protected]
Subject: st: question on keeping observations - selecting substitute instituions for sampled institutions
Dear List users,
I am trying to collect a sample out of schools. I have successfully
sampled 300 institutions out of 4000. I have now a dataset containing
4000 observations and a variable named sample indicating whether a given
institution is part of my sample (code=1) or not (code=0).
As I also need 2 substitutes for each institutions I would like to chose
the ones that are right above and under the sampled school. Is there a
simple way to do this with stata? I was browsing through the Keep
observations commands but didn’t manage to find out how to do this.
Thank U in advance
Annamaria
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