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st: RE: RE: RE: summation (+ absolute value) formula


From   "Scott Merryman" <smerryman@kc.rr.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: RE: summation (+ absolute value) formula
Date   Tue, 7 Nov 2006 17:23:15 -0600

Nick,

Thanks - I over looked that.

But I think I misinterpreted the question.  If only the last three time
periods are to be summed, then what I originally had is the last three
periods of the cumulative sum over the entire time span.  Instead, I believe
this should work:

bysort id (t): gen foo = sum(abs((pip - l.pip)/l.pip)) if t >  t[_N -3]

Scott


> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
> Sent: Tuesday, November 07, 2006 5:09 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: RE: summation (+ absolute value) formula
> 
> In a panel, I guess the second -replace- should
> be -by id:- also. Otherwise _N has the interpretation
> of the number of observations in the dataset, not
> in each panel.
> 
> Nick



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