Not an answer but I find that
DF <- data.frame(let = letters[1:3], num = 1:3,
stringsAsFactors = FALSE)
is very handy. Damn it, if I want a factor I'll tell the machine I do :)
Or you can also set this option globally with
options(stringsAsFactors = TRUE)
Gabor Grothendieck warns that this last can possibly cause problems when using
R programs from other places. I ran into this problem once with reshape.
--- On Thu, 10/9/08, Michael Kubovy <[EMAIL PROTECTED]> wrote:
> From: Michael Kubovy <[EMAIL PROTECTED]>
> Subject: Re: [R] Turn factors to numeric
> To: "Charilaos Skiadas" <[EMAIL PROTECTED]>
> Cc: "r-help" <r-help@r-project.org>
> Received: Thursday, October 9, 2008, 8:25 AM
> Dear R-helpers,
>
> The FAQ in question says:
>
> > It may happen that when reading numeric data into R
> (usually, when
> > reading in a file), they come in as factors. If f is
> such a factor
> > object, you can use
> > as.numeric(as.character(f))
> > to get the numbers back. More efficient, but harder to
> remember, is
> >
> > as.numeric(levels(f))[as.integer(f)]
>
> I wonder why the R Core group did not choose to make such a
> useful
> operation simpler for the user (i.e., something like a
> factor2numeric() function that would be a wrapper to the
> more
> efficient command).
> _____________________________
> Professor Michael Kubovy
> University of Virginia
> Department of Psychology
> USPS: P.O.Box 400400 Charlottesville, VA 22904-4400
> Parcels: Room 102 Gilmer Hall
> McCormick Road Charlottesville, VA 22903
> Office: B011 +1-434-982-4729
> Lab: B019 +1-434-982-4751
> Fax: +1-434-982-4766
> WWW: http://www.people.virginia.edu/~mk9y/
>
> On Oct 9, 2008, at 7:16 AM, Charilaos Skiadas wrote:
>
> > R-FAQ 7.10:
> >
> http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-do-I-convert-factors-to-numeric_003f
> >
> > On Oct 9, 2008, at 6:59 AM, joseph kambeitz wrote:
> >
> >> I am having some problems while trying to fit
> simple data.
> >> I aggregated some data using:
> >> data1 <- aggregate(data1$T2,
> list=(SOA=data1$SOA), mean)
> >>
> >> unfortunatly this coerces my variable SOA into a
> factor. Therefore
> >> when a afterwards try to fit a simple equation to
> my variable T2
> >> using a formula on SOA i get a error because SOA
> is a factor and
> >> that "*" is not meaningful for
> factors...
> >>
> >> nls(T2 ~ a + b*SOA, start=list(a=1,b=1),
> data=data1, trace=TRUE)
> >>
> >> In fact SOA is a numeric variable (in my
> experiments it is the time
> >> that passed!) so i would like to re-coerce it into
> a numeric
> >> variable to do the fit or to find a method to do
> the fit even
> >> though SOA is a factor. Thanks a lot for your
> help!
> >>
> >> Best
> >> Jokel
>
> [[alternative HTML version deleted]]
>
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