[R] String variables in GLM

[Thomas Lumley]

On Tue, 11 Sep 2001 Marcos_Sanches at gallup.com wrote:

>
> 	Hello!
> 	I have a dataset with variables in string format (ages class and sex) which
> I want to recode as numerical variables. How can I accomplish this?  Is
> there any way to do that automatically? Could someone help me?
>

You probably want factor variables. These are described in Section 4 of
the 'Introduction to R' manual.

Reading variables in using read.table will typically make them into
factors automatically. If you have string variables use factor() to
convert them
eg

  sex<-factor(sex,levels=c("Male","Female"))

The variable can then be used in regression modelling where it will by
default be coded with indicator variables for each level except the first
(in this case that corresponds to Male=0, Female=1).


	-thomas


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