[R] factor, as.factor and levels

[Heinz Tuechler]

Dear All,

to my surprise as.factor does not accept a levels argument. Maybe I 
did not read the documentation well enough. See the example below. I 
wanted to use ch1 as factor in the newdata argument of survfit, so I 
assumed that I could write as.factor(ch1, levels=ch1), since the 
order should be kept.

But as.factor(ch1, levels=ch1) results in the error:

Error in as.factor(ch1, levels = ch1) :
   unused argument(s) (levels = c("low", "inter", "high"))

factor(ch1, levels=ch1) works as I expected.
Is it intended that as.factor does not use the levels argument?

Thanks,

Heinz

ch1 <- c('low', 'inter', 'high')
factor(ch1)
factor(ch1, levels=ch1)
as.factor(ch1, levels=ch1)

 > version
                _
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status         Patched
major          2
minor          8.1
year           2009
month          03
day            13
svn rev        48132
language       R
version.string R version 2.8.1 Patched (2009-03-13 r48132)
 > sessionInfo()
R version 2.8.1 Patched (2009-03-13 r48132)
i386-pc-mingw32

locale:
LC_COLLATE=German_Switzerland.1252;LC_CTYPE=German_Switzerland.1252;LC_MONETARY=German_Switzerland.1252;LC_NUMERIC=C;LC_TIME=German_Switzerland.1252

attached base packages:
[1] splines   stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] survival_2.34-1 car_1.2-12      gmodels_2.14.1  gdata_2.4.2
[5] Hmisc_3.5-2

loaded via a namespace (and not attached):
[1] cluster_1.11.12 grid_2.8.1      gtools_2.5.0-1  lattice_0.17-20
[5] MASS_7.2-46
 >