[R] coding for categorical variables with unequal observations

[Nordlund, Dan (DSHS/RDA)]

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,

Dan

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,
> 
> Dan
> 
> Daniel J. Nordlund
> Research and Data Analysis
> Washington State Department of Social and Health Services
> Olympia, WA  98504-5204
>  
>  
> 
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