[R] performance question

Thomas W Blackwell tblackw at umich.edu
Fri Sep 26 17:52:17 CEST 2003

Axel  -

I believe that a function argument is not literally copied
until the first time it is modified within the function.
See email exchanges on this list from/to Ross Boylan within
the month of September for a more authoritative answer to
this question.  (Do you know about the R-help archives at
three sites listed on  http://cran.R-project.org/search.html ?)

-  tom blackwell  -  u michigan medical school  -  ann arbor  -

On Fri, 26 Sep 2003, Axel Benz wrote:

> I am about to write functions for multivariate kernel densitiy estimation
> with mixed categorical and continuous date (accoring to Jeff Racine and Qi
> Li), and the leave-one-out window esitmation needs a lot of computation.
> I am now optimizing the code performance and therefore fhe following
> questions:
> As R uses call-by-value for functions, is it computational expensive to pass
> large matrices in function arguments?
> (i.e. are they really copied and does this need much computing time?) Is it
> maybe better to work with locally visible variables and nested functions in
> the optimized code?
> I have already used Rprof (and I could speed up the code a lot by the
> information from Rprof), but it does not tell me about that.
> Thank you for your hints!
> Axel
> ________________________________________
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> Arbeitswirtschaft und Organisation (IAO)
> Dipl. Inf. Axel Benz
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