Re: st: data management help

[Richard Williams <Richard.A.Williams.5@nd.edu>]

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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