[R] Still trying to avoid loops

[Tom Wright]

No problem with disguise, I'm looking for pretty.

On Wed, 2015-02-04 at 12:06 -0800, Bert Gunter wrote:
> tapply() (of which by() is essentially a wrapper) **is** a (disguised)
> loop (at the R level, of course).
> 
> Cheers,
> Bert
> 
> 
> 
> Bert Gunter
> Genentech Nonclinical Biostatistics
> (650) 467-7374
> 
> "Data is not information. Information is not knowledge. And knowledge
> is certainly not wisdom."
> Clifford Stoll
> 
> 
> 
> 
> On Wed, Feb 4, 2015 at 11:49 AM, Rui Barradas <ruipbarradas at sapo.pt> wrote:
> > Hello,
> >
> > Aren't the levels of your example wrong? If the levels are
> > levels=c('a','b','c'), not c('b', 'a', 'c'), then the following will do the
> > job.
> >
> > unname(unlist(tapply(dat$D, dat$S, order)))
> >
> >
> > Hope this helps,
> >
> > Rui Barradas
> >
> > Em 04-02-2015 19:34, Tom Wright escreveu:
> >>
> >> Given a dataframe:
> >>
> >> dat<-data.frame(S=factor(c(rep('a',2),rep('b',1),rep('c',3)),levels=c('b','a','c')),
> >>                 D=c(5,1,3,2,3,4))
> >>
> >> where S is a subject identifier and D a visit (actually a date in my
> >> real dataset). I would like to generate another column giving the visit
> >> number
> >>
> >> R=c(2,1,1,1,2,3)
> >>
> >> My current solution uses nested loops and is slow and ugly. I've looked
> >> at by() but can't see how to keep the order of R correct.
> >>
> >> Thanks,
> >> Tom
> >>
> >> ______________________________________________
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> >> 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.
> >>
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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.