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RE: st: Aggregate constant to scalar and local


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Aggregate constant to scalar and local
Date   Fri, 13 Oct 2006 12:27:20 +0100

Uli is right. -_pctile- is faster than -summarize, detail-
to get the median. But, interestingly, not much: a few
quick experiments indicate ~10% faster. The story, 
presumably, is that most of the work is in the sorting, 
and the fact that -summarize, detail- calculates so much 
more is secondary. 

Nick 
n.j.cox@durham.ac.uk 

Ulrich Kohler
 
> Gawrich Stefan wrote:
> > I want to obtain aggregate values (e.g. median age by sex) from an
> > individual data set and generate locals out of them (to 
> show the values in
> > a textbox in a graph).
> 
> Others have proposed different solutions. Here is one that 
> tries to be fast:
> 
> . _pctile age if sex==1
> . local female_medage = r(r1)
> . _pctile age if sex==2
> . local female_medage = r(r1)
> 
> or, slighly more general:
> 
> . levelsof sex, local(K)
> . foreach k of local K {
> .	_pctile age if sex == `k'
> .	local medage`k' = `r1'
> . }
> 
> (This produces local macros medage1 and medage2)
> 
> 
> The major lesson to be learned from this and the other 
> solutions is to work 
> with "saved results" (See -help return-, or chapter 4 in 
> Kohler/Kreuter "Data 
> Analysis Using Stata") 

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