[R] Still trying to avoid loops

[David L Carlson]

How about?

> ave(dat$D, dat$S, FUN=order)
[1] 2 1 1 1 2 3
> ave(dat_2$D, dat_2$S, FUN=order)
[1] 2 2 1 1 1 3

Note, your answer for the second example is incorrect since row 2 (c, 3) and row 5 (c, 2) are both assigned 2.

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Tom Wright
Sent: Wednesday, February 4, 2015 2:08 PM
To: Rui Barradas
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] Still trying to avoid loops

Thanks, I was not aware of order().
I did deliberately mess up the order of S. The following example breaks
your solution
dat_2<-data.frame(S=factor(c('a','c','a','b','c','c')),
		  D=c(5,3,1,3,2,4))

which should give the answer c(2,2,1,1,2,3)

Your solution does indicate that sorting the data correctly before
starting might solve the problem.


On Wed, 2015-02-04 at 19:49 +0000, Rui Barradas 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('a','b','a','c','c','c',levels=c('b','a','c')),
> > 		D=c(1,5,3,2,3,4))
> >
> > 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
> >
> > ______________________________________________
> > 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.
> >

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