Perfect!

EG

On 6/21/07, Dimitris Rizopoulos <dimitris.rizopoulos@med.kuleuven.be> wrote:
>
> maybe you want to use ave(), e.g.,
>
> f$sums <- ave(f$b, f$e, FUN = sum)
>
>
> I hope it helps.
>
> Best,
> Dimitris
>
> ----
> Dimitris Rizopoulos
> Ph.D. Student
> Biostatistical Centre
> School of Public Health
> Catholic University of Leuven
>
> Address: Kapucijnenvoer 35, Leuven, Belgium
> Tel: +32/(0)16/336899
> Fax: +32/(0)16/337015
> Web: http://med.kuleuven.be/biostat/
>      http://www.student.kuleuven.be/~m0390867/dimitris.htm
>
>
> ----- Original Message -----
> From: "Economics Guy" <economics.guy@gmail.com>
> To: <r-help@stat.math.ethz.ch>
> Sent: Thursday, June 21, 2007 3:53 PM
> Subject: [R] generating a new variable based on results of a by
> command
>
>
> >I have a matrix with a set of variables one of which is a factor.
> >Using by()
> > I have calculated something about each group (say the sum). Now I
> > want to
> > create a new variable in the original matrix that contains the
> > results of
> > the by() for each observation that is in the corresponding group.
> >
> > For example I have:
> >
> > ---------
> >
> > a <-c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16)
> >
> > b <-c(7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22)
> >
> > e
> > <-c("A","B","C","D","E","F","A","B","C","D","E","F","D","E","F","A")
> >
> > f <-data.frame(e,a,b)
> >
> > # Calculate sum by group
> >
> > sums <- by(f, e, function(x) sum(x$b))
> >
> > -----------
> >
> > Now I would like to assign each observation in f a new variable
> > based on the
> > results of the by(). I converted sums into a matrix and then tried
> > using
> > match() and ifthen() but could not get it to work.
> >
> > Thanks,
> >
> > EG
> >
> > [[alternative HTML version deleted]]
> >
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> >
>
>
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