Hi Ista, I was doing about something similar when I saw your post, so I took your code and did some timings:
> system.time(replicate(1000000, count.0 <- length(which(x == 0)))) user system elapsed 5.590 0.173 5.834 > system.time(replicate(1000000, count.1 <- sum(x == 0))) user system elapsed 5.043 0.064 5.095 > all.equal(count.0, count.1) [1] TRUE > sessionInfo() R version 2.15.2 Patched (2012-10-31 r61060) Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit) locale: [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods base So there is some time difference there ;-) Best, Jorge.- On Sat, Jan 5, 2013 at 2:43 AM, Ista Zahn <> wrote: > Hi Sam, > > Here is one alternative, which is at least faster: > > system.time(count.0 <- length(which(x == 0))) > system.time(count.1 <- sum(x == 0)) > all.equal(count.0, count.1) > > Best, > Ista > > On Fri, Jan 4, 2013 at 10:30 AM, Sam Steingold <> wrote: > > Hi, > > to count vector elements with some property, the standard idiom seems to > > be length(which): > > --8<---------------cut here---------------start------------->8--- > > x <- c(1,1,0,0,0) > > count.0 <- length(which(x == 0)) > > --8<---------------cut here---------------end--------------->8--- > > however, this approach allocates and discards 2 vectors: a logical > > vector of length=length(x) and an integer vector in which. > > is there a cheaper alternative? > > Thanks! > > > > -- > > Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X > 11.0.11103000 > > http://www.childpsy.net/ http://iris.org.il http://honestreporting.com > > http://jihadwatch.org http://pmw.org.il > http://www.PetitionOnline.com/tap12009/ > > War doesn't determine who's right, just who's left. > > > > ______________________________________________ > > 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. > [[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.
