On 07/06/2012 10:27, Rui Barradas wrote:
Hello,
To my great surprise, on my system, Windows 7, R 15.0, 32 bits, an R
version is faster!
Faster than what? diag() is written entirely in R, just more general
than yours and so one would expect it to be slower.
I have to say that we don't see a fast identity as a priority, as it
almost always can be eliminated from calculations, and for large
matrices one would want to use a sparse representation such as package
Matrix.
Rdiag <- function(n){
m <- matrix(0, nrow=n, ncol=n)
m[matrix(rep(seq_len(n), 2), ncol=2)] <- 1
m
}
Rdiag(4)
n <- 5e3
t1 <- system.time(d1 <- diag(n))
t2 <- system.time(d2 <- Rdiag(n))
all.equal(d1, d2)
rbind(diag=t1, Rdiag=t2, ratio=t1/t2)
Anyway, why don't you create it once, save a copy and use it many times?
Hope this helps,
Rui Barradas
Em 07-06-2012 08:55, Ceci Tam escreveu:
Hello, I am trying to build a large size identity matrix using diag().
The
size is around 23000 and I've tried diag(23000), that took a long time.
Since I have to use this operation several times in my program, the
running
time is too long to be tolerable. Are there any alternative for diag(N)?
Thanks
Cheers,
yct
[[alternative HTML version deleted]]
______________________________________________
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.
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________
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.
