[R] Still trying to avoid loops

[Tom Wright]

Sorry Jim,
That messes up on S=='a'. Should be 2,1 not 1,2

Neat answer though and looks like it should be pretty quick after I
apply some sorting.

On Wed, 2015-02-04 at 15:37 -0500, jim holtman wrote:
> >
> 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))
> > dat
>   S D
> 1 a 5
> 2 a 1
> 3 b 3
> 4 c 2
> 5 c 3
> 6 c 4
> > dat$visit <- ave(seq(nrow(dat)), dat$S, FUN = seq_along)
> > dat
>   S D visit
> 1 a 5     1
> 2 a 1     2
> 3 b 3     1
> 4 c 2     1
> 5 c 3     2
> 6 c 4     3
> 
> 
> 
> 
> Jim Holtman
> Data Munger Guru
>  
> What is the problem that you are trying to solve?
> Tell me what you want to do, not how you want to do it.
> 
> On Wed, Feb 4, 2015 at 3:08 PM, Tom Wright <tom at maladmin.com> wrote:
>         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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>         > >>
>         > >
>         > > ______________________________________________
>         > > 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.
>         
>         ______________________________________________
>         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.
>         
> 
>