Another way is 

reg<-lapply(split(data,data$byvar),lm,formula=y~x)
 
Justin BEM
Elève Ingénieur Statisticien Economiste
BP 294 Yaoundé.
Tél (00237)9597295.



----- Message d'origine ----
De : Chuck Cleland <ccleland@optonline.net>
À : Alvaro <apisilva@esalq.usp.br>
Cc : r-help@stat.math.ethz.ch
Envoyé le : Mercredi, 15 Novembre 2006, 23h58mn 09s
Objet : Re: [R] Regression


Alvaro wrote:
> I need to run a regression analysis with a large number of samples. Each
> sample (identified in the first file column) has its own x and y values. I
> will use the same model in all samples. How can I run the model for each
> sample? In SAS code I would use the "BY SAMPLE" statement.

  Here are a couple of ways:

by(warpbreaks, warpbreaks$tension, function(x) lm(breaks ~ wool, data = x))

library(nlme)

summary(lmList(breaks ~ wool | tension, warpbreaks))

?by

?lmList

>  
> 
> Alvaro
> 
>  
> 
>  
> 
> 
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> 
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> 

-- 
Chuck Cleland, Ph.D.
NDRI, Inc.
71 West 23rd Street, 8th floor
New York, NY 10010
tel: (212) 845-4495 (Tu, Th)
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______________________________________________
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