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Re: st: RE: Dropping all subjects but those in the last period


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: RE: Dropping all subjects but those in the last period
Date   Mon, 8 Apr 2013 20:50:49 +0100

As Elan implies, Stata is very good at such problems. There is
certainly no need for intricate choreography with files. Here is
another solution:

bysort id (year) : drop if year[_N] < 2000

Nick
njcoxstata@gmail.com

On 8 April 2013 20:39, Cohen, Elan <cohened@upmc.edu> wrote:

> Let's assume 2010 is the "last year".  Then:
>
> egen flag = total(year==2010), by(id)
> drop if !flag

Miguel Angel Duran

> My dataset includes observations for about 9000 companies per year in a
> twenty years period. To clean the dataset, I would like to drop all those
> companies that are not present in the last year (because the rest went
> bankrupt or were absorbed), but I do not know how to do it. Can this be done
> just by splitting the datasets by period and then merging them?  Each
> company has the same id across years.
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