> -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Peter Alspach > Sent: Wednesday, May 20, 2009 10:02 PM > To: milton ruser; Chloe Smith > Cc: r-help@r-project.org > Subject: Re: [R] Problems with sample variance > > Thanks Milton - I misread Chloe's original question. > > nSims <- 1000 > sampSiz <- 15 > myVars <- tapply(rnorm(nSims*sampSiz), rep(1:nSims, sampSiz), var) > > This is a little more succinct, although I do not know enough about > random number generation to be certain about the effect of breaking a > single call to rnorm into 1000 bits, rather than having 1000 calls to > rnorm (or even if there is such an effect. Comment anyone?).
It doesn't matter whether you use a single call or multiple calls, the same set of numbers will be generated either way (if one starts with the same seed). > > It used to be (and I imagine still is) not efficient > incrementally grow > an object in a loop [as is done in your code with variance.list <- > c(variance.list, var(mysample))]. Better to create > variance.list at its > full size first (filled with NA) and then populate it. Not that it is > likely to make too much difference with these numbers. > > HTH ..... > > Peter Alspach Hope this is helpful, Dan Daniel Nordlund Bothell, WA USA ______________________________________________ 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.
