[R] Problem with data.frames

[kjetil brinchmann halvorsen]

On 4 Aug 2003 at 11:09, Simon Fear wrote:

> Peter is right, but there is a point here: it would be nice if
> attach(my.dframe) would do nothing - or at least warn - if my.dframe was
> already in the search list. Like library(). Attaching twice is almost
> bound
> to be an error?

Not necessarily. If you changed the data --- as when debugging a data 
file and repeatedly sourcing it in --- you need to attach repeatedly. 
Of course, you should detach() first, but that is not a requirement 
today.

Kjetil Halvorsen

> Of course in many circumstances it might be better to use with() than
> attach() - if you haven't come across with(), it works like attach()
> with an
> inbuilt detach() when the parentheses close.
> 
> Aside 1: it would also be nice if ?attach pointed to ?with. Is this kind
> of
> suggestion best sent to r-help or r-devel?
> 
> Aside 2: is with() efficient, or does it create a copy of the dataset? 
> 
> SF
> 
> 
> -----Original Message-----
> From: Peter Dalgaard BSA [mailto:p.dalgaard at biostat.ku.dk]
> Sent: 04 August 2003 00:52
> To: Andreas Eckner
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] Problem with data.frames
> 
> 
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> ________________________________________________________________
> 
> Andreas Eckner <andreas.eckner at soundinvest.net> writes:
> 
> > Hi,
> > 
> > I just encountered a problem in R that may easily be fixed: If one
> uses
> > attach for a data.frame e.g. 10000 times and forgets detach, then R
> gets
> > incredibly slow (less then 10% of the original speed).
> 
> R also gets incredibly slow if you create 10000 copies of your data
> set, which is effectively the same thing! The fix is: Don't do that... 
> 
> -- 
>    O__  ---- Peter Dalgaard             Blegdamsvej 3  
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
> 
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> 
> Simon Fear
> Senior Statistician
> Syne qua non Ltd
> Tel: +44 (0) 1379 644449
> Fax: +44 (0) 1379 644445
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