|From||"b. water" <firstname.lastname@example.org>|
|Subject||Re: st: help with understanding syntax 'gen last=_n==_N'|
|Date||Mon, 28 Nov 2005 09:13:19 +0000|
From: Sergio Correia <email@example.com>_________________________________________________________________
Subject: Re: st: help with understanding syntax 'gen last=_n==_N'
Date: Sun, 27 Nov 2005 22:15:25 -0500
the -by- prefix repeats the command for each possible value of "study".
So, using _N returns the total number of obs. for each value of study.
_n returns the observation index (1,2,3,4..) within each value of study
Finally, _n=_N is true when the index is at its last position.
On 11/27/05, b. water <firstname.lastname@example.org> wrote:
> dear listers,
> i am trying to understand one of the do-files application for stata. one of
> the lines read:
> qui by study: gen last=_n==_N
> my understanding so far: this is quietly, sort according to study, and as a
> result, to generate a variable last fulfilling this condition _n==-N.
> although i have the output, i would like to know what in general does gen
> last=_n==_N do?
> thank you,
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