[R] rbind and data.frame

[Liaw, Andy]

Are you sure that the time difference is *only* in creating the data frame,
rather than other computations in the loop?

Andy

> -----Original Message-----
> From: Göran Broström [mailto:gb at stat.umu.se]
> Sent: Friday, December 07, 2001 7:25 AM
> To: Prof Brian Ripley
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] rbind and data.frame
> 
> 
> On Fri, 7 Dec 2001, Prof Brian Ripley wrote:
> 
> > On Fri, 7 Dec 2001, [iso-8859-1] Göran Broström wrote:
> > 
> > > On Wed, 5 Dec 2001, Göran Broström wrote:
> > >
> > > [...]
> > >
> > > > My real problem is how to create a data frame in a 
> sequentially growing
> > > > manner, when I know the final size (no of cases). I 
> want to avoid to
> > > > call 'rbind' many times, and instead create an 'empty' 
> data frame in
> > > > one call, and then fill it. Are there better ways of doing this?
> > >
> > > Got no answer to this one, so I provide one myself:
> > 
> > The usual answer is to create a data frame of the desired size and
> > populate it via indexing.  That's in some books I know!
> 
> I know that book too (thanks!). I did what you suggest, and 
> that took 7 
> hours to run. Definitely.
> 
> Göran
> 
> > >
> > > The answer is: Yes, definitely. I did this, with pure  R  
> code, and
> > > created a new data frame with around 58000 records. It 
> took 7 hours to
> > > run. I then did it with compiled code (Fortran), and that 
> made a slight
> > > difference:  It took 4.8 seconds(!).
> > >
> > > Göran
> > >
> > > 
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> -- 
>  Göran Broström                      tel: +46 90 786 5223
>  professor                           fax: +46 90 786 6614
>  Department of Statistics            http://www.stat.umu.se/egna/gb/
>  Umeå University
>  SE-90187 Umeå, Sweden             e-mail: gb at stat.umu.se
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