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lapply() not converting columns to factors (no error message)

2 messages · A Singh, Peter Dalgaard

Original
A Singh
# 
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.
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
----------------------
A Singh
Aditi.Singh at bristol.ac.uk
School of Biological Sciences
University of Bristol
Peter Dalgaard
#
A Singh wrote:
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.