Wolfgang Raffelsberger wrote:
Dear list,
I'm wondering how to optimize functions/processes like the one shown
below (which simplifies something we're trying to do with very large
datasets).
In many cases I've noticed that using apply, sapply etc can help
speeding up processes, but in this case I don't see how I could do so.
a <- runif(10000000,0.5,1.6)
C <- 2
M <- 10000000
system.time( for (i in 1:(M-1)) {C <- C* c(a[i],a[i+1])} )
Well, in principal you could say:
a <- runif(10000000,0.5,1.6)
C <- 2
M <- 10000000
system.time(C <- C * c(prod(a[-M]), prod(a[-1])))
but this is all completely inaccurate from a numerical point of view -
and you probably end up with c(0, 0) which is the quickest way to
calculate those numbers in similar accurate way.
Uwe Ligges
By the way, I'm using R-2.7.2 on Win XP and/or Fedora Linux.
Thank's in advance for any hints,
Wolfgang Raffelsberger
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wolfgang Raffelsberger, PhD
Laboratoire de BioInformatique et Génomique Intégratives
CNRS UMR7104, IGBMC 1 rue Laurent Fries, 67404 Illkirch Strasbourg,
France
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
