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st: Re: re: counter variable


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: re: counter variable
Date   Sat, 2 May 2009 17:23:25 +0200

<>

You have to hand it to all contributors here, though, that this is not your everyday, apply-bysort-straightforwardly-and-look-at-Nick`s-column- in -the-SJ-carefully problem (see http://www.stata-journal.com/sjpdf.html?articlenum=pr0004). The fact that you want this thing sorted, but not counted, by schoolyear and counted, but not sorted, by the new dummy, makes this quite involved, and despite my best effort, I cannot find a one liner for it that does not make extensive use of -cond-. So kudos to Eva for her two liner :-)


HTH
Martin
_______________________
----- Original Message ----- From: "Kit Baum" <baum@bc.edu>
To: <statalist@hsphsun2.harvard.edu>
Sent: Saturday, May 02, 2009 4:49 PM
Subject: st: re: counter variable


<> T suggested

 g newvar = 1 if new_prc==1
 bys Id (schlyr): replace newvar = newvar[_n-1]+1 if newvar !=1

This sounds to me like a generally bad idea. The first statement just changes the new_prc zero values into missing values. The second statement relies upon the fact that missing is a value not equal to 1. Although the logic works, I think Eva's suggested approach is a better way to think about a problem like this (although I deplore her reliance on -set varabbrev on-, which is IMHO a Very Bad Idea).

Kit Baum | Boston College Economics & DIW Berlin | http://ideas.repec.org/e/pba1.html An Introduction to Stata Programming | http://www.stata-press.com/books/isp.html An Introduction to Modern Econometrics Using Stata | http://www.stata-press.com/books/imeus.html



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