Re: [R] for-loop with multiple variables changing

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Mon 06 Feb 2006 - 23:24:34 EST

Sean Davis <sdavis2@mail.nih.gov> writes:

> On 2/6/06 5:53 AM, "Piet van Remortel" <piet.vanremortel@gmail.com> wrote:
>
> > Hi all,
> >
> > Never really managed to build a for-loop with multiple running
> > variables in an elegant way.
> >
> > Can anybody hint ?
> >
> > See below for an example of what I would like.
> >
> > EXAMPLE
> > a<-c(1,2,3)
> > b<-c("name1","name2","name3")
> >
> > for( number in a, name in b ) {
> > print( number ) ##take a value
> > print( name ) ##and have its name available from a second list
> > }
> >
> > Does R support this natively ?
>
> I'm not sure what language does support this construct natively? In any
> case, what about:

(Genstat has (had?) a "parallel for" structure, I believe.)  

> for (j in a) {
> print(a[j])
> print(b[j])
> }

I think you mean "for (i in 1:3) {...}".

Also, check out the mapply() construct for related functionality.

> You may be thinking of a "hash" structure. If you are, you could look at
> using lists. See the R-intro on using list data structures.
>
> Sean

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Mon Feb 06 23:48:48 2006

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