Thomas Lumley wrote: >> So it looks as though sum(c(...)) is somwhow independent of >> the order of its arguments, which implies that the summation >> it does is not quite the addition corresponding to "+". >> >> I now feel out of my depth, so hope someone else knows/can >> find the truth about this! > > sum() uses a long double accumulator.
BTW, summing numbers is (surprisingly?) actually a quite interesting problem. See, for example, the paper ‘A Comparison Of Methods For Accurate Summation’ by John Michael McNamee for some nice example. The paper is available online at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.103.344&rep=rep1&type=pdf -- Karl Ove Hufthammer ______________________________________________ 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.
