Re: st: Expanding single observation data to create unbalanced panel data set-up

[Jeph Herrin <junk@spandrel.net>]

Assume you have four variables  -country-, -warid-, -start-, and -end-
which contain the country, an identifier for the war, the start year
and the end year.

Then if I understand your data and problem correctly

 gen length=2004-start+1
 expand length
 bys country warid : gen year=start+_n-1
 bys country year  : egen war=max(inrange(year,start,end))
 bys country year  : keep if _n==1

should do it.

hope this helps,
Jeph


Geoffrey Wallace wrote:
> I have a civil war data set that contains a single observation for each 
> war, including start year, end year, and other conflict-level variables 
> for all wars that were ongoing or began between 1988 and 2004. My 
> objective is to expand this data set into a panel format with separate 
> annual observations for both the war and post-war periods, while all 
> years before the war started are excluded. So for a war lasting 
> 1990-1992, this means there would be no observations for 1988-1989, but 
> then observations for the war years 1990-1992 as well as postwar years 
> 1993-2004.
>
> A complicating factor is that some countries experience several separate 
> wars during this period, each of which has a unique id. I want to make 
> sure I don’t create duplicate observations for those cases, but rather 
> have a simple indicator variable with “1” when a country is experiencing 
> war and “0” for the post-war period.
>
> My question is whether anyone can suggest a relatively efficient way for 
> producing such a data set.
>
> I’ve thought of manually going through the data and including a variable 
> indicating the number of years for the relevant war and post-war period, 
> then using the –expand– command to create the larger data set, and then 
> somehow reformatting it afterward for indicate each relevant year for 
> the war and post-war periods. However, I was wondering if there was a 
> more straightforward way to do this.
>
> Thanks for your consideration.
>
> Geoff
>
> -
> Geoffrey Wallace
> PhD Candidate
> Department of Government
> 214 White Hall
> Cornell University
> Ithaca, NY 14853
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