Your -while- syntax is not going to work the way
you want if only because -while- is not going to loop
over observations unless you tell it to. There are
other reasons why it would not work, but let's set
those aside.
In some circumstances when you want to work backwards,
you are best off creating a variable which is MINUS the year
and sorting on that first.
In this case, the time order doesn't appear central
to what you're doing, so a solution looks like
su B if country == "Belgium", meanonly
replace B = `r(mean)' * C if mi(B) & Country == "Belgium"
There is an FAQ on this subject also at
http://www.stata.com/support/faqs/data/missing.html
Nick
[email protected]
Dev Vencappa
> Stata users, I have the following data set
>
> year B C Country
> 1995 . x Belgium
> 1996 . x Belgium
> 1997 . x Belgium
> 1998 . x Belgium
> 1999 x x Belgium
> 2000 . x Belgium
> 2001 . x Belgium
> 2002 . x Belgium
>
> Variable B has data for only 1999 and missing for other
> years. I want to extrapolate missing years using variable C,
> which is some kind of multiplicative scalar that varies over
> the years. Writing a command like the following seems to work
> fine to fill missing values after year 1999:
>
> replace B=B[_n-1]*C if B==. & year>1999 & country=="Belgium"
>
> However, the following does not seem to work (or at least
> fills the missing value for the year 1998 only):
>
> replace B=B[_n+1]*C if B==. & year<1999
>
> I believe this is because Stata works only forward and not
> backward. Is there a way to ask Stata to work backwards
> starting with the value from the year 1999 and repeat the
> command for prior years? I have tried the following loop
> command but that does not seem to work either (this command
> does not even fill in the missing value for the year 1998,
> for obvious reasons)
>
> while B[_n+1]!=. & B==. & country=="Belgium"{
> replace B=B[_n+1]*C
> }
>
> I think I am missing a syntax of Stata here.
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