[R] as.logical(factor) behaviour

[R Help]

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
<phgrosjean at 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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