Thank you for the reference to Knuth. Indeed in vol. 2 he has a > -----Original Message----- > From: Tony Plate [mailto:[EMAIL PROTECTED] > Sent: Friday, September 24, 2004 8:05 AM > To: Vadim Ogranovich > Subject: Re: [Rd] algorithm reference for sample() > > Have you tried looking in Knuth's books on computer > algorithms? (They are classics for good reason!) If I > remember correctly, a colleague found a very clever and fast > algorithm for just this problem in one of those volumes. > > -- Tony Plate > > > At Thursday 06:48 PM 9/23/2004, Vadim Ogranovich wrote: > >Hi, > > > >Don't know if it belongs to r-devel or r-help, but since I > am planning > >to alter some of R's internal code I am sending it here. > > > >The existing implementation of the sample() function, when > the optional > >'prob' argument is given, is quite inefficient. The complexity is > >O(sampleSize * universeSize), see ProbSampleReplace() and > >ProbSampleNoReplace() in random.c. This makes the function > impractical > >for the vector sizes I use. I want to re-code these functions and I > >"think" I can come up with a more efficient algorithm. > However before I > >go and reinvent the wheel I wonder if there is a published > description > >of an efficient sampling algorithm with user-specified probabilities? > > > >Thanks, > >Vadim > > > > [[alternative HTML version deleted]] > > > >______________________________________________ > >[EMAIL PROTECTED] mailing list > >https://stat.ethz.ch/mailman/listinfo/r-devel > >
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