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st: RE: Re: counting and eliminating data


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Re: counting and eliminating data
Date   Wed, 25 Jan 2006 17:09:48 -0000

Note that use of the -egen- function -nvals()- 
depends on prior installation of the -egenmore-
package from SSC. 

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

Michael Blasnik
 
> There are a couple of approaches you could take, but I think 
> using egen 
> nvals is the best bet.
> 
> sort subarea
> by subarea: egen nyears=nvals(year)
> keep if nyears>=13
> sort subarea
> by subarea: egen firstfive=nvals(year) if year<=5
> by subarea: egen lastfive=nvals(year) if year>21
> * fill out missing values within subarea
> bysort subarea (firstfive): replace firstfive=firstfive[1]
> bysort subarea (lastfive): replace lastfive=lastfive[1]
> keep if firstfive>=2 & lastfive>=2
> drop nyears firstfive lastfive

Jennifer Devine
 
> > Can someone please set me in the right direction for coding 
> a program to 
> > count and eliminate data if it doesn't meet a certain criteria?
> >
> >  I have survey data taken over 26 years and the survey area 
> is divided 
> > into subareas. I want to only include a subarea if data was 
> collected 13 
> > years out of the 26 and data must have been collected 2 
> years of the first 
> > 5 years and 2 years of the last 5 years. If the subarea 
> does not meet that 
> > criteria, I want Stata to drop that subarea from the 
> analysis. At the 
> > moment, I'm having to look at everything individually and 
> it takes several 
> > days to eliminate subareas.

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