The problem is that, underneath the factors are actually numbers (1
and 2), where as, if you extract the levels and then get the logical,
it converts them to strings and then to logicals. I run into this
problem ALL THE TIME with numerics in a dataset. Consider the
following:
> factor(c(3,6,5,2,7,8,4))
[1] 3 6 5 2 7 8 4
Levels: 2 3 4 5 6 7 8
> as.numeric(factor(c(3,6,5,2,7,8,4)))
[1] 2 5 4 1 6 7 3
> as.numeric(as.character(factor(c(3,6,5,2,7,8,4))))
[1] 2 3 4 5 6 7 8
as.logical converts all non-zeros to TRUE, and 0 to false:
> as.logical(0:10)
[1] FALSE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
Hope that helps,
Sam
On Sun, Aug 15, 2010 at 5:32 AM, Philippe Grosjean
<phgrosj...@sciviews.org> wrote:
> Hello,
>
> According to ?as.logical:
>
> "as.logical attempts to coerce its argument to be of logical type. For
> factors, this uses the levels (labels)."
>
> However,
>
>> as.logical(factor(c("FALSE", "TRUE")))
> [1] TRUE TRUE
>
> Shouldn't it be the same as:
>
>> as.logical(levels(factor(c("FALSE", "TRUE"))))
> [1] FALSE TRUE
>
> according to the documentation? Did I miss something here?
>
>> sessionInfo()
> R version 2.11.1 RC (2010-05-29 r52140)
> x86_64-apple-darwin9.8.0
>
> locale:
> [1] C/UTF-8/C/C/C/C
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
> Thanks,
>
> Philippe
> --
> ..............................................<°}))><........
> ) ) ) ) )
> ( ( ( ( ( Prof. Philippe Grosjean
> ) ) ) ) )
> ( ( ( ( ( Numerical Ecology of Aquatic Systems
> ) ) ) ) ) Mons University, Belgium
> ( ( ( ( (
> ..............................................................
>
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