R help - Nov 2009 - lapply() not converting columns to factors (no error message)

Dear List,

I'm having a curious problem with lapply(). I've used it before to
convert
a subset of columns in my dataframe, to factors, and its worked. But now, 
on re-running the identical code as before it just doesn't convert the 
columns into factors at all.

As far as I can see I've done nothing different, and its strange that it 
shouldn't do the action.

Has anybody come across this before? Any input on this strange issue much 
appreciated..

Hope I haven't missed something obvious.

Thanks a lot,

Aditi

(P.s.- I've tried converting columns one by one to factors this time, and 
that works.
>P1L55<-factor(P1L55)
>levels(P1L55)
>[1] "0" "1"
Code:

prm<-read.table("P:\\.....  .csv", header=T, ...sep=",",
...)

prmdf<-data.frame(prm)

prmdf[2:13]<-lapply(prmdf[2:13], factor) ## action performed, no error 
message

##I tried to pick random columns and check
>levels(P1L55)
>NULL
>is.factor(P1L96)
>FALSE

----------------------
A Singh
Aditi.Singh at bristol.ac.uk
School of Biological Sciences
University of Bristol

Sorry, my file is at:


http://www.4shared.com/file/153147281/a5c78386/Testvcomp10.html


----------------------
A Singh
Aditi.Singh at bristol.ac.uk
School of Biological Sciences
University of Bristol

Works for me:

x <-
read.csv(url("http://dc170.4shared.com/download/153147281/a5c78386/Testvcomp10.csv?tsid=20091116-075223-c3093ab0"))
names(x)
x[2:13] <- lapply(x[2:13], factor)
> levels(x$P1L55)
[1] "0" "1"
> is.factor(x$P1L96)
[1] TRUE
> sessionInfo()
R version 2.10.0 (2009-10-26)
i386-apple-darwin9.8.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

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

other attached packages:
[1] lattice_0.17-26

loaded via a namespace (and not attached):
[1] grid_2.10.0  tools_2.10.0

On Mon, Nov 16, 2009 at 4:50 AM, A Singh <Aditi.Singh at bristol.ac.uk>
wrote:
> Sorry, my file is at:
>
>
> http://www.4shared.com/file/153147281/a5c78386/Testvcomp10.html
>
>
> ----------------------
> A Singh
> Aditi.Singh at bristol.ac.uk
> School of Biological Sciences
> University of Bristol
>
> ______________________________________________
> 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.
>

A Singh wrote:
> Dear List,
> 
> I'm having a curious problem with lapply(). I've used it before to
> convert a subset of columns in my dataframe, to factors, and its worked.
> But now, on re-running the identical code as before it just doesn't
> convert the columns into factors at all.
> 
> As far as I can see I've done nothing different, and its strange that
it
> shouldn't do the action.
> 
> Has anybody come across this before? Any input on this strange issue
> much appreciated..
> 
> Hope I haven't missed something obvious.
> 
> Thanks a lot,
> 
> Aditi
> 
> (P.s.- I've tried converting columns one by one to factors this time,
> and that works.
> 
>> P1L55<-factor(P1L55)
>> levels(P1L55)
>> [1] "0" "1"
> 
> Code:
> 
> prm<-read.table("P:\\.....  .csv", header=T,
...sep=",", ...)
> 
> prmdf<-data.frame(prm)
> 
> prmdf[2:13]<-lapply(prmdf[2:13], factor) ## action performed, no error
> message
> 
> ##I tried to pick random columns and check
> 
>> levels(P1L55)
>> NULL
> 
>> is.factor(P1L96)
>> FALSE
Make sure that you are looking in the same object that you changed. E.g.

attach(prmdf)
prmdf[2:13]<-lapply(prmdf[2:13], factor)
levels(P1L55)

is not going to work

levels(prmdf$P1L55)

should, or attaching _after_ the change. Also, make sure that you don't
have P1L55 et al. sitting in the global enviromnent.

-- 
   O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907