st: Re: counting and eliminating data

["Michael Blasnik" <michael.blasnik@verizon.net>]

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

Michael Blasnik

----- Original Message ----- 
From: "Jennifer Devine" <jdevine@mun.ca>
To: <statalist@hsphsun2.harvard.edu>
Sent: Wednesday, January 25, 2006 8:34 AM
Subject: st: counting and eliminating data



> 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.
>
> Thank you,
> Jennifer
>
>
>
> Jennifer Devine
> Doctoral Candidate
> Memorial University of Newfoundland
> St. John's, NL A1C 5S7
> Canada
> Tel: (709) 737-8833
> Fax: (709) 737-3121
>
> email: jdevine@mun.ca
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