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
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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
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