The original method is faster than which.max for longish numeric vectors (in R-2.15.1), but you should check time and memory usage on your own machine:
> x <- runif(18e6) > system.time(for(i in 1:100)which(x>0.99)[1]) user system elapsed 11.64 1.05 12.70 > system.time(for(i in 1:100)which.max(x>0.99)) user system elapsed 16.38 2.94 19.35 Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of Jeff Newmiller > Sent: Wednesday, September 19, 2012 8:06 AM > To: Mike Spam; [email protected] > Subject: Re: [R] effective way to return only the first argument of "which()" > > ?which.max > --------------------------------------------------------------------------- > Jeff Newmiller The ..... ..... Go Live... > DCN:<[email protected]> Basics: ##.#. ##.#. Live Go... > Live: OO#.. Dead: OO#.. Playing > Research Engineer (Solar/Batteries O.O#. #.O#. with > /Software/Embedded Controllers) .OO#. .OO#. rocks...1k > --------------------------------------------------------------------------- > Sent from my phone. Please excuse my brevity. > > Mike Spam <[email protected]> wrote: > > >Hi, > > > >I was looking for a function like "which()" but only returns the first > >argument. > >Compare: > > > >x <- c(1,2,3,4,5,6) > >y <- 4 > >which(x>y) > > > >returns: > >5,6 > > > >which(x>y)[1] > >returns: > >5 > > > >which(x>y)[1] is exactly what i need. I did use this but the dataset > >is too big (~18 mio. Points). > >That's why i need a more effective way to get the first element of a > >vector which is bigger/smaller than a specific number. > > > >I found "match()" but this function only works for equal numbers. > > > > > > > >Thanks, > >Nico > > > >______________________________________________ > >[email protected] 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. > > ______________________________________________ > [email protected] 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. ______________________________________________ [email protected] 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.
