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Re: st: data management help


From   Richard Williams <Richard.A.Williams.5@nd.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: data management help
Date   Sun, 03 Oct 2004 23:29:24 -0500

At 12:09 AM 10/4/2004 -0400, mnitkin wrote:
I have a data set with 131,000 firm observations over 14 years. Individual firms may be in the data set between 1 and 14 times. I want to keep only those firms that have observations for the entire 14 year period.

I've tried all the tricks I know as well as a number of suggestions on the stata website, but I haven't had any luck.
Something like this might do it. Lets suppose you want to keep those cases where the same id number occurs 14 times (i.e. there is a first occurrence and then 13 "duplicates"). Lets further assume each firm has a maximum of 1 record per year. Then,

duplicates tag id, gen(nyears)
keep if nyears == 13


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Richard Williams, Notre Dame Dept of Sociology
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