I wrote:
> However, as far as I understand, this can be done with
>
> . by firmid, sort: gen nyears = _N
> . keep if nyears == 14
>
> where "firmid" is the idenfier variable for the firms and "years" is the
> variable holding the year of observation.
Or, in one-line:
. by firmid, sort: keep if _N == 14
many regards
uli
> mnitkin wrote:
> > Your assumptions about the data are correct.
> >
> > I tried your suggestion, but "duplicates" is not a valid command on my
> > version of Stata. Is there a similar command that might work with pre
> > 7.0 versions of Stata.
> > Thanks for the help,
> > Mindy
> >
> > Richard Williams wrote:
> > > 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
> > >
> > >
> > > -------------------------------------------
> > > Richard Williams, Notre Dame Dept of Sociology
> > > OFFICE: (574)631-6668, (574)631-6463
> > > FAX: (574)288-4373
> > > HOME: (574)289-5227
> > > EMAIL: [email protected]
> > > WWW (personal): http://www.nd.edu/~rwilliam
> > > WWW (department): http://www.nd.edu/~soc
> > >
> > > *
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> >
> > *
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