hits=0.5 tests=BAYES_00,ETHZ_GEOCITIES,FORGED_RCVD_HELO
X-USF-Spam-Flag: NO
try this:
distance2 <- function (x1, x2) {
temp <- x1 - x2
sum(temp * temp)
}
x1 <- rnorm(1e06)
x2 <- rnorm(1e06)
system.time(for (i in 1:100) distance2(x1, x2))
system.time(for (i in 1:100) crossprod(x1 - x2))
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Jason Liao" <[EMAIL PROTECTED]>
To: <r-help@r-project.org>
Sent: Thursday, January 31, 2008 3:28 AM
Subject: [R] fastest way to compute the squared Euclidean distance
betweentwo vectors in R
>I have a program which needs to compute squared Euclidean distance
> between two vectors million of times, which the Rprof shows is the
> bottleneck. I wondered if there is any faster way than my own simple
> function
>
> distance2 = function(x1, x2)
> {
> temp = x1-x2
> sum(temp*temp)
> }
>
> I have searched the R-help archives and can not find anything except
> when the arguments are matrices. Thanks for any lead.
>
> Jason
>
> Jason Liao, http://www.geocities.com/jg_liao
> Associate Professor of Biostatistics
> Drexel University School of Public Health
> 1505 Race Street, Mail Stop 1033
> Bellet Building, 6th Floor
> Philadelphia, PA 19102
> phone 215-762-3934
>
>
>
> ____________________________________________________________________________________
> Looking for last minute shopping deals?
>
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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