Re: st: help with understanding syntax 'gen last=_n==_N'

["b. water" <barleywater@hotmail.com>]

thank you to both nick (cox) and sergio for the explanations. it was clearer 
with worked example.

regards,
bw



> From: Sergio Correia <sergio.correia@gmail.com>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: statalist@hsphsun2.harvard.edu
> 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.
>
> Sergio
>
>
> On 11/27/05, b. water <barleywater@hotmail.com> 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,
> > bw
> >
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