On Wed, 18 Aug 2004, Göran Broström wrote:
> On Wed, Aug 18, 2004 at 09:30:50AM +0100, Prof Brian Ripley wrote:
> > On Wed, 18 Aug 2004, Göran Broström wrote:
> >
> > > I'm trying a recommendation on the help page for 'factor':
> > >
> > > > x <- c(1, 2, 1, 2)
> > > > x <- factor(x, labels = c("one", "two"))
> > > > x
> > > [1] one two one two
> > > Levels: one two
> > > > as.numeric(levels(x))[x]
> > > [1] NA NA NA NA
> > > Warning message:
> > > NAs introduced by coercion
> > >
> > > Also,
> > >
> > > > as.numeric(as.character(x))
> > > [1] NA NA NA NA
> > > Warning message:
> > > NAs introduced by coercion
> > >
> > > What am I doing wrong? This is R-1.9.1, Linux (debian installation)
> >
> > Your factor is made up of "one", "two", which are not numeric -- don't
> > expect R to speak English (or Swedish). You could just as easily have
> > used labels = c("apples", "oranges").
>
> Didn't work either. :-)
>
> I really want the underlying numeric codes (convert the variable to numeric).
> 'as.integer(x)' seems to do the trick, is that correct? Also 'as.numeric(x)',
> although it is "meaningless" according to the help page.
as.integer is OK, but unclass() is the usual way (it doesn't lose the
other attributes such as names).
x <- factor(1:10)
names(x) <- letters[1:10]
> as.integer(x)
[1] 1 2 3 4 5 6 7 8 9 10
> unclass(x)
a b c d e f g h i j
1 2 3 4 5 6 7 8 9 10
attr(,"levels")
[1] "1" "2" "3" "4" "5" "6" "7" "8" "9" "10"
> > > Another question: I have a factor with four levels, which I want
> > > to collapse to two. How do I do it in the simplest possible way?
> >
> > via levels<- : there is an example on the help page for levels.
>
> Thanks; exactly what I was looking for.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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