Re: [R] Matrix of dummy variables from a factor

From: Doran, Harold <HDoran_at_air.org>
Date: Wed 07 Dec 2005 - 09:01:54 EST


Good point. Probably not for any subsequent use in R. But, I work in an org that uses SAS, HLM, SPSS, among others. As a part of our control processes at times we replicate analyses in different software programs. For instance, we will replicate lmer functions using HLM. But, HLM requires a matrix of dummy variables. So, I have used R to create this matrix for use in another software package that does need it.

-----Original Message-----
From: r-help-bounces@stat.math.ethz.ch
[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Berton Gunter Sent: Tuesday, December 06, 2005 4:27 PM To: 'Liaw, Andy'; 'Charles H. Franklin'; r-help@stat.math.ethz.ch Subject: Re: [R] Matrix of dummy variables from a factor

But note: There are (almost?) no situations in R where the dummy variables coding is needed. The coding is (almost?) always handled properly by the modeling functions themselves.

Question: Can someone provide a "straightforward" example where the dummy variable coding **is** explicitly needed?

"The business of the statistician is to catalyze the scientific learning process." - George E. P. Box    

> -----Original Message-----
> From: r-help-bounces@stat.math.ethz.ch
> [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Liaw, Andy
> Sent: Tuesday, December 06, 2005 12:30 PM
> To: 'Charles H. Franklin'; r-help@stat.math.ethz.ch
> Subject: Re: [R] Matrix of dummy variables from a factor
>
> See ?model.matrix.
>
> HTH,
> Andy
>
> From: Charles H. Franklin
> >
> > 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@polisci.wisc.edu
> > chfrankl@wisc.edu
> > 608-263-2022 (voice)
> > 608-265-2663 (fax)
> >
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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Dec 07 09:10:09 2005

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