[R] Matrix of dummy variables from a factor

[John Fox]

Dear Charles,

Try model.matrix(~f)[,-1].

Regards,
 John

--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
-------------------------------- 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Charles H. Franklin
> Sent: Tuesday, December 06, 2005 3:03 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Matrix of dummy variables from a factor
> 
> What is a simple way to convert a factor into a matrix of 
> dummy variables?
> 
> fm<-lm(y~f)
> 
> where f is a factor takes care of this in the estimation. I'd 
> like to save the result of expanding f into a matrix for later use.
> 
> Thanks.
> 
> Charles
> 
> -- 
> 
> 
>  Charles H. Franklin
>  Professor, Political Science
>  University of Wisconsin, Madison
>  franklin at polisci.wisc.edu
>  chfrankl at wisc.edu
>  608-263-2022 (voice)
>  608-265-2663 (fax)
> 
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