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Re: st: data management help


From   Ulrich Kohler <kohler@wz-berlin.de>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: data management help
Date   Mon, 4 Oct 2004 09:11:10 +0200

A similar command called -dups- is available for Stata 7 on the SSC-Archive. 
To install type

. ssc install dups

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.

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:  Richard.A.Williams.5@ND.Edu
> > WWW (personal):    http://www.nd.edu/~rwilliam
> > WWW (department):    http://www.nd.edu/~soc
> >
> > *
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>
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-- 
kohler@wz-berlin.de
+49 (030) 25491-361


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