[R] coding for categorical variables with unequal observations
Nordlund, Dan (DSHS/RDA)
NordlDJ at dshs.wa.gov
Thu Apr 3 23:58:55 CEST 2008
Ignore the previous post. I completely spaced out on which mailing list I was reading and thought this was a SAS question. My apologies, I'll just crawl back into my hole. :-)
Obviously not helpful,
Daniel J. Nordlund
Research and Data Analysis
Washington State Department of Social and Health Services
Olympia, WA 98504-5204
> -----Original Message-----
> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] On Behalf Of Nordlund,
> Dan (DSHS/RDA)
> Sent: Thursday, April 03, 2008 2:45 PM
> To: yata at wustl.edu; r-help at r-project.org
> Subject: Re: [R] coding for categorical variables with
> unequal observations
> > -----Original Message-----
> > From: r-help-bounces at r-project.org
> > [mailto:r-help-bounces at r-project.org] On Behalf Of Tanya Yatsunenko
> > Sent: Thursday, April 03, 2008 1:55 PM
> > To: r-help at r-project.org
> > Subject: [R] coding for categorical variables with unequal
> > observations
> > Hi,
> > I am doing multiple regression, and have several X
> variables that are
> > categorical.
> > I read that I can use dummy or contrast codes for that, but
> are there
> > any special rules when there're unequal #observations in each
> > groups (4
> > females vs 7 males in a "gender" variable)?
> > Also, can R generate these codes for me?
> > THanks.
> You don't need to do anything special, and yes you can just
> let SAS do it for you. For most of the regression PROCs you
> can put your categorical variables in a CLASS statement.
> Depending on which procedure you are using, you may be able
> to specify whether you want effects or dummy coding, and
> which level of the categorical variable should be the
> "comparison" level. It is also possible to use PROC GLMMOD
> to create your design variables to be fed into other PROCs.
> Other approaches are possible as well.
> If you provide more detail on what analyses you plan to
> undertake, someone may be able to provide more specific advice.
> Hope this is helpful,
> Daniel J. Nordlund
> Research and Data Analysis
> Washington State Department of Social and Health Services
> Olympia, WA 98504-5204
> R-help at r-project.org mailing list
> PLEASE do read the posting guide
> and provide commented, minimal, self-contained, reproducible code.
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