Tyr this: > system.time(sort(x, partial=c(999999,1000000))) user system elapsed 0.12 0.00 0.14
On Fri, Sep 4, 2009 at 3:53 AM, ONKELINX, Thierry<thierry.onkel...@inbo.be> wrote: > Using tail() for the selection is more elegant and slightly faster. > >> N<- 1000000 >> x <- runif(N) >> system.time(x[order(x)[c(N-1,N)]]) > user system elapsed > 1.08 0.01 1.10 >> system.time(sort(x)[c(N-1,N)]) > user system elapsed > 0.36 0.00 0.35 >> system.time(tail(sort(x), 2)) > user system elapsed > 0.33 0.00 0.33 > > > HTH, > > Thierry > > ---------------------------------------------------------------------------- > ir. Thierry Onkelinx > Instituut voor natuur- en bosonderzoek / Research Institute for Nature and > Forest > Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, > methodology and quality assurance > Gaverstraat 4 > 9500 Geraardsbergen > Belgium > tel. + 32 54/436 185 > thierry.onkel...@inbo.be > www.inbo.be > > To call in the statistician after the experiment is done may be no more than > asking him to perform a post-mortem examination: he may be able to say what > the experiment died of. > ~ Sir Ronald Aylmer Fisher > > The plural of anecdote is not data. > ~ Roger Brinner > > The combination of some data and an aching desire for an answer does not > ensure that a reasonable answer can be extracted from a given body of data. > ~ John Tukey > > -----Oorspronkelijk bericht----- > Van: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > Namens andrew > Verzonden: vrijdag 4 september 2009 4:24 > Aan: r-help@r-project.org > Onderwerp: Re: [R] Easy way to get top 2 items from vector > > it is speedier to use sort than a combination of [] and order: > > N<- 1000000 > x <- runif(N) >> system.time(x[order(x)[c(N-1,N)]]) > user system elapsed > 1.03 0.00 1.03 >> system.time(sort(x)[c(N-1,N)]) > user system elapsed > 0.28 0.00 0.28 > > > > On Sep 4, 11:17 am, Noah Silverman <n...@smartmediacorp.com> wrote: >> Phil, >> >> That's perfect. (For my application, I've never seen a tie. While >> possible, the likelihood is almost none.) >> >> Thanks! >> >> -- >> Noah >> >> On 9/3/09 4:29 PM, Phil Spector wrote: >> >> >> >> > Noah - >> > max(x[-which.max(x)] will give you the second largest value, but >> > it doesn't handle ties. >> > x[order(x,decreasing=TRUE)[n]] will give you the nth largest >> > value, with the same caveat regarding ties. For example, >> > x[order(x,decreasing=TRUE)[1:3]] will give you the three largest >> > values. >> >> > - Phil Spector >> > Statistical Computing Facility >> > Department of Statistics >> > UC Berkeley >> > spec...@stat.berkeley.edu >> >> > On Thu, 3 Sep 2009, Noah Silverman wrote: >> >> >> Hi, >> >> >> I use the max function often to find the top value from a matrix or >> >> column of a data.frame. >> >> >> Now I'm looking to find the top 2 (or three) values from my data. >> >> >> I know that I could sort the list and then access the first two >> >> items, but that seems like the "long way". Is there some way to >> >> access "max_2" or similar? >> >> >> Thanks! >> >> >> -- >> >> Noah >> >> >> ______________________________________________ >> >> r-h...@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-h...@r-project.org mailing >> listhttps://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting >> guidehttp://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. > > Druk dit bericht a.u.b. niet onnodig af. > Please do not print this message unnecessarily. > > Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer > en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd > is > door een geldig ondertekend document. The views expressed in this message > and any annex are purely those of the writer and may not be regarded as > stating > an official position of INBO, as long as the message is not confirmed by a > duly > signed document. > > ______________________________________________ > 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ 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.
