st: Re: loop to fill in missing observations

["Li Chuntao" <chtl@econ.hku.hk>]

Dear Fabrizio,

   As you need four observations for each country and year, you can turn 
the year and election to a quarter variable, that is, treat the first obs 
for each year as spring and the second as summer. then you have two 
variables to identify each election, that is, country and season.

then you can use the fillin command in stata.

suppose you have the following data, where X is the variable to be the same 
with the previous observation


  country   season    x
        1        1    1
        1        2    4
        2        1    5
        2        2    8
        2        3   10
        3        1    4
        4        1    3
        4        2    5

fillin country season

then u got the following data


  country   season    x   _fillin
        1        1    1         0
        1        2    4         0
        1        3    .         1
        2        1    5         0
        2        2    8         0
        2        3   10         0
        3        1    4         0
        3        2    .         1
        3        3    .         1
        4        1    3         0
        4        2    5         0
        4        3    .         1

is this what you need?

Cheers

Chuntao




----- Original Message ----- 
From: "Fabrizio Gilardi" <Fabrizio.Gilardi@unil.ch>
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, June 15, 2007 10:25 PM
Subject: st: loop to fill in missing observations



> Dear Statalist,
>
> I have a dataset of national elections in 28 countries. Observations  are 
> elections. This means that there can be several elections in the  same 
> year, and on the other hand only years when an election was held  are 
> included in the dataset.
>
> I want to fill in missing years for each country. My idea was to loop 
> over countries and years to check for every country if a given year  is 
> present, and if not fill it in. To do so, I have created an  appropriate 
> number of missing observations to be filled in, and a  counter variable to 
> identify them.
>
> Concretely, the dataset looks like this:
>
> countryn year elecn fillin
> 1 1990 1 .
> 1 1994 2 .
> 1 1994 3 .
> 1 1997 4 .
> 2 1989 1 .
> 2 1992 2 .
> 2 1995 3 .
> 2 1999 4 .
> 2 2000 5 .
> . . . 1
> . . . 2
> . . . 3
>
>
> And my code is the following:
>
> g n=.
> local z=1
> qui forval x=1/28 {
> forval y=1975/2002 {
> sum year if year==`y' & countryn==`x'
> replace n=r(N)
> replace year=`y' if n==0 & fillin==`z'
> replace countryn=`x' if n==0 & fillin==`z'
> count if countryn==`x' & year==`y' & fillin==`z'
> local w=r(N)
> local z=`z'+`w'
> }
> }
>
> Now, for some countries it works fine, but for most some missing  years 
> are not filled in. It does not seem to depend on whether in the  country 
> there was more than one election in some year, and I cannot  find any 
> pattern that could help me identify the problem.
>
> What am I doing wrong?
>
> Many thanks in advance,
>
> Fabrizio
>
>
> ------------------------------------------------------------
> Fabrizio Gilardi, PhD
> Institut d'Etudes Politiques et Internationales
> Universit� de Lausanne
> B�timent Anthropole
> CH-1015 Lausanne
> Switzerland
> Phone +41 21 692 31 48
> Fax + 41 21 692 31 45
> fabrizio.gilardi@unil.ch
> http://wwwpeople.unil.ch/fabrizio.gilardi/
> ------------------------------------------------------------
>
>
>
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