I don't know what you mean by 'the latest release', but R does not behave this way in a vanilla session in 2.6.0 or R-patched. Had you given the 'at a minimum' information asked for in the posting guide, we might have been able to deduce what the problem is. I get
> x1 <- c(1:4,4,4,4) > f <- factor(x1) > levels(f) [1] "1" "2" "3" "4" > as.numeric(levels(f)) [1] 1 2 3 4 > as.numeric(levels(f))[as.integer(f)] [1] 1 2 3 4 4 4 4 My guess is that your session has a package attached that is corrupting as.numeric. This is known to happen under certain circumstances: see https://stat.ethz.ch/pipermail/r-help/2007-October/142367.html for a warning about not re-installing packages when upgrading: most likely you have used one of the packages which make as.numeric S4 generic and installed it in R < 2.6.0. On Mon, 12 Nov 2007, Alun Pope wrote: > Unfortunately it is not quite as simple as this. Agreed, as the possibility of user error needs to be taken into account. > It seems (to me) that > the change to the behaviour of as.numeric() in the latest release means > that the advice given in FAQ 7.10 (and the help) is incorrect when the > factor levels are integers. The following example illustrates: Factor levels should always be character, and are in your example. >> x1 <- c(1:4,4,4,4) >> f <- factor(x1) >> levels(f) > [1] "1" "2" "3" "4" >> as.numeric(levels(f))[as.integer(f)] #this is pasted from FAQ 7.10 > Error in UseMethod("as.double") : no applicable method for "as.double" >> as.integer(levels(f))[as.integer(f)] > [1] 1 2 3 4 4 4 4 > > And (not surprisingly) the other FAQ 7.10 recommendation behaves the > same way. > > Even more unfortunate is the fact that packages may also be affected. > Yhis seems to be the case for example with spdep, in which the function > nb2listw() contains statements of the form > > mode(x) <- "numeric" > > which I assume is what is causing that function to fail with the same > error message as above. I shall post separately to the list for spdep. > > Alun > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On Behalf Of Matthew Keller > Sent: Wednesday, 7 November 2007 8:04 AM > To: Alexandre Santos > Cc: r-help@r-project.org > Subject: Re: [R] Problem with a non-factor,non-numeric variable in a > data.frame > > Alexandre, > > Try rereading FAX 7.10, it explains why as.numeric() won't do it: > > "In any case, do not call as.numeric() or their likes directly for the > task at hand as as.numeric() or unclass() give the internal codes" > > I.e., the INTERNAL CODE of the factor is what as.numeric() is working > on rather than the numeric representation that you see. > > > > On 11/6/07, Alexandre Santos <[EMAIL PROTECTED]> wrote: >> I tested >> >> as.numeric(as.character(Ratio)) >> >> and it works perfectly! >> >> I still don't get why as.numeric(Ratio) was not enough, but at least >> now I know how to deal with it. >> >> Thanks for the tip, and sorry for missing the R-FAQ issue 7.10. >> >> Cheers, >> Alexandre Santos >> >> >> 2007/11/6, John Kane <[EMAIL PROTECTED]>: >>> Have a look at the R-FAQ issue 7.10. It's a standard >>> problem >>> >>> For more information about your variable try >>> >>> str(variable). >>> >>> >>> --- Alexandre Santos <[EMAIL PROTECTED]> >>> wrote: >>> >>>> Dear R list, >>>> >>>> I would like to perform an ANOVA in a set of >>>> measurements, but I have >>>> problems formatting the data. >>>> >>>> The data is a two dimensional array containing two >>>> columns: >>>> - "Stim" : the type of stimulation (string) >>>> - "Ratio" : a ratio of two numeric values >>>> >>>> Now, because some values are missing in the data >>>> (defaulting to zero), >>>> part of this array will be populated with NA ratios. >>>> Maybe this is >>>> important later. >>>> >>>> In order to make the ANOVA analysis, I need to turn >>>> my vector into a data.frame. >>>> >>>> I tried vector.table=as.data.frame(vector) >>>> >>>> But I realized that >>>> is.numeric(Ratio) gives FALSE >>>> is.factor(Ratio) gives TRUE >>>> >>>> After reading the documentation, I tried >>>> >>>> vector.table=as.data.frame(vector, stringsAsFactors >>>> = FALSE) >>>> >>>> This time >>>> >>>> is.numeric(Ratio) gives FALSE >>>> is.factor(Ratio) gives FALSE >>>> >>>> So I don't even know what is Ratio, but it's not yet >>>> numeric (is this >>>> due to the NA values?). >>>> >>>> How can I get R to understand that Ratio is numeric? >>>> Checking the >>>> documentation it seems you can do it with I(x), but >>>> the details are >>>> not explained. I also tried as.numeric(Ratio), and >>>> everything was >>>> turned into zeros. >>>> >>>> Any suggestions? >>>> >>>> Cheers, >>>> >>>> Alexandre Santos >>>> >>>> Neuro-MPI, Martinsread, Germany -- 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 ______________________________________________ R-help@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.
