On Dec 9, 2009, at 12:00 AM, Peng Yu wrote:
On Tue, Dec 8, 2009 at 10:37 PM, David Winsemius <dwinsem...@comcast.net
> wrote:
On Dec 8, 2009, at 11:28 PM, Peng Yu wrote:
I have the following code, which tests the split on a data.frame and
the split on each column (as vector) separately. The runtimes are of
10 time difference. When m and k increase, the difference become
even
bigger.
I'm wondering why the performance on data.frame is so bad. Is it a
bug
in R? Can it be improved?
You might want to look at the data.table package. The author calinms
significant speed improvements over dta.frames
This bug has been found long time back and a package has been
developed for it. Should the fix be integrated in data.frame rather
than be implemented in an additional package?
What bug?
David.
system.time(split(as.data.frame(x),f))
user system elapsed
1.700 0.010 1.786
system.time(lapply(
+ 1:dim(x)[[2]]
+ , function(i) {
+ split(x[,i],f)
+ }
+ )
+ )
user system elapsed
0.170 0.000 0.167
###########
m=30000
n=6
k=3000
set.seed(0)
x=replicate(n,rnorm(m))
f=sample(1:k, size=m, replace=T)
system.time(split(as.data.frame(x),f))
system.time(lapply(
1:dim(x)[[2]]
, function(i) {
split(x[,i],f)
}
)
)
______________________________________________
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PLEASE do read the posting guide
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and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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.
