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RE: st: repeated values of a variable


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: repeated values of a variable
Date   Wed, 17 Mar 2004 10:17:54 -0000

Note that 

. bysort id : drop if _N == 1 

is (nearly) equivalent. It's more direct; 
but note the side-effect of -sort-ing. 

Nick 
n.j.cox@durham.ac.uk 

Richard Williams

> >>Is there a way to have Stata identify observations that 
> have equivalent
> >>values for a given variable?  Speficically, I want to trim 
> my dataset to
> >>individuals that live in the same household using a household id
> >>variable.  I want to get rid of those that live alone.  I 
> tried using
> >>the egen tag and egen group commands, but that did not help.
> >
> >Is this what you want?
> >
> >. egen x = count(id), by(id)
> >
> >. drop if x==1
> 
> To follow up -- if id is missing, x gets coded 0.  So, if you 
> have missing 
> data on the id variable, and you also want such cases 
> dropped, a better 
> coding would be
> 
> . egen x = count(id), by(id)
> 
> . keep if x > 1

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