[R] Newbie struggling with "factors"

[John Fox]

Dear Jonathan and Tom,

At 10:10 AM 3/29/2002 -0500, Jonathan Baron wrote:
>On 03/29/02 05:58, Tom Arnold wrote:
>
> >When I query R about the field, it
> >tells me it is class "factor"
> >
> >> class(n$OSUSE)
> >[1] "factor"
> >> mode(n$OSUSE)
> >[1] "numeric"
>
>I'm surprised at this.  I would think it would be character.

Factors are numeric vectors of class factor, with the level information 
given by a levels attribute; for example:

     > fac <- factor(rep(c("a", "b"), 2))
     > fac
     [1] a b a b
     Levels:  a b

     > unclass(fac)
     [1] 1 2 1 2
     attr(,"levels")
     [1] "a" "b"

     > class(fac)
     [1] "factor"

     > mode(fac)
     [1] "numeric"
     >

Regards,
  John
-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
-----------------------------------------------------

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