On Fri, 25 Jun 2004, Douglas Grove wrote: > I get ties in output from runif() when I generate as few as 10^5 > variates and get quite a lot when I generate 10^6. Is this > expected??
It should have been. > I haven't seen any duplication with rnorm(10^6), but > see varying amounts of duplication using rexp(), rbeta() and > rgamma(). I would have thought that there'd be enough precision > that one wouldn't get ties until generating samples larger than this.. Did you do the calculations? Please do so. There are about 2e9 possible values of the standard generators. > qbirthday(classes=2e9) [1] 52655 Statisticians ought to know about the birthday problem! (rnorm is different because the default generator uses two uniforms, deliberately to increase the precision.) > > set.seed(222) > > sum(duplicated(runif(10^5))) > [1] 4 That's unusually high, BTW. > > sum(duplicated(runif(10^6))) > [1] 140 -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html