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Re: st: Fill in values for year in an unbalanced panel with known order


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Fill in values for year in an unbalanced panel with known order
Date   Tue, 23 Oct 2012 17:19:05 +0100

This is a variation on a standard problem, on which see

FAQ     . . . . . . . . . . . . . . . . . . . . . . . Replacing missing values
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        1/12    How can I replace missing values with previous or
                following nonmissing values or within sequences?
                http://www.stata.com/support/faqs/data-management/
                replacing-missing-values/

I suggest

sort id, stable
by id: replace year = cond(month == 1, year[_n-1] + 1, year[_n-1]) if
missing(year)

Nick

On Tue, Oct 23, 2012 at 5:07 PM, Fernando Luco
<flucoestatalist@gmail.com> wrote:

> I'm trying to fill in the year of observations for which I know the
> month and because of the order, I have no doubt about the year.
> However, the year was not recorded. In particular, the data looks as
> follows
>
> id year month
> 1 1988 5
> 1 . 6
> 1 . 7
> 1 . 8
> 1 . 9
> 1 . 10
> 1 . 11
> 1 . 12
> 1 . 1
> 1 1989 2
> 1 1989 3
> 1 . 4
> 2 . 3
> 2 1989 4
> 2 1989 5
> 2 . 6
> 2 . 7
> 2 . 8
> 2 1989 9
> 2 . 10
> 2 . 11
> 2 . 12
> 2 . 1
> 2 1990 2
> 2 . 3
>
> So, it is an unbalanced panel, that for each id might start and end at
> a different year month combination, and I know that the order of the
> observations within id is correct, so I'm sure that the first
> observation for id==2 is of 1989 while the second observation that has
> id==2 and month==3 (the last observation in the example) corresponds
> to 1990. The main complication is that for some people I might have a
> gap of more than one year between observations, which has made things
> difficult. I would like to use the structure of the data to fill in
> the data for year.
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