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Re: st: indexing for first non-missing value


From   Scott Merryman <scott.merryman@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: indexing for first non-missing value
Date   Wed, 15 May 2013 06:52:30 -0500

egen firstyear = min(year), by(id)

Scott

On Wed, May 15, 2013 at 6:46 AM, James Bernard <jamesstatalist@gmail.com> wrote:
> Hi all,
>
> I have been dealing with a dataset where I need to copy the value of
> the first non-missing value of one variable to create a new variable
> called first year observed:
>
> id             year                                 first year observed
> -------      ------------
> -----------------------------
> A              .                                               1996
> A              1996                                          1996
> A              1997                                          1996
> A              1998                                          1996
> A                 .                                             1996
> A                 .                                             1996
> B               1998                                         1998
> B               1999                                          1998
> B                   .                                            1998
> B                   .                                            1998
>
>
> Going through Stata discussions, I found out that one way is to use indexing
>
> bysort id: gen first_year_observed=year[1]
>
> where the bracket indicates the first non-missing value
>
> But this find only the first value, be it missing or non-missing. Is
> there any simple indexing way?
>
>
> Thanks,
> James
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