factor, as.factor and levels

It is just a simple version of 'factor'.  The only speed advantage it
might have is that it checks to see if it is a factor first.  Here is
the definition:

)> as.factor
function (x)
if (is.factor(x)) x else factor(x)
<environment: namespace:base>

You can always list out what the function does to get a better
understanding of how it works.

On Wed, Apr 8, 2009 at 8:16 AM, Heinz Tuechler <tuechler at gmx.at> wrote:

Thank you, Jim. I see, the fact that in the documentation you find only
"as.factor(x)" means that it does not accept more arguments.
Does as.factor have speed advantages over factor, or is there a different
cause for it's existence?

Heinz



At 13:50 08.04.2009, jim holtman wrote:

as.factor does not accept levels as an argument.  use the first form
that you have

factor(ch1, levels=ch1)



On Wed, Apr 8, 2009 at 7:36 AM, Heinz Tuechler <tuechler at gmx.at> wrote:

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

--
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

--
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?