[R] Factor to numeric conversion - as.numeric(as.character(f))[f] - Language definition seems to say to not use this.

[Ista Zahn]

Hi Mathew,

In what way are they at odds?

On Mon, Apr 1, 2013 at 1:48 PM, Matthew Lundberg
<matthew.k.lundberg at gmail.com> wrote:
> These two seem to be at odds.  Is this the case?
>
> >From help(factor) - section Warning:
>
> To transform a factor f to approximately its original numeric values,
> as.numeric(levels(f))[f] is recommended and slightly more efficient than
> as.numeric(as.character(f)).
>
> >From the language definition - section 2.3.1:
>
> Factors are currently implemented using an integer array to specify the
> actual levels and
> a second array of names that are mapped to the integers. Rather
> unfortunately users often
> make use of the implementation in order to make some calculations easier.
> This, however,
> is an implementation issue and is not guaranteed to hold in all
> implementations of R.
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.