I think you want to look at sum(x)/2066.758 - 1
which on my Linux box is 2.2e-16. -roger Brahm, David wrote: > After upgrading to R-2.3.1 on Linux Redhat, I was suprised by this: > > R> x <- c(721.077, 592.291, 372.208, 381.182) > R> sum(x) - 2066.758 > [1] 4.547474e-13 > > Now I understand that floating point arithmetic is not precise, but > 1) the result is exactly 0 in R-2.2.1 (patched) on the same machine, > 2) .Machine$double.eps = 2.2e-16, so the error seems quite large. > > Also note I get the same result on R-2.3.1 under Windows, and that > R> (721.077 + 592.291 + 372.208 + 381.182) - 2066.758 > [1] 0 > > Is this related to the (2.3.0) NEWS item: > sum(), prod(), mean(), rowSums() and friends use a long double > accumulator where available and so may be more accurate. > and should I be concerned? Thanks. > > -- David Brahm ([EMAIL PROTECTED]) > > > Version: > platform = i686-pc-linux-gnu > arch = i686 > os = linux-gnu > system = i686, linux-gnu > status = > major = 2 > minor = 3.1 > year = 2006 > month = 06 > day = 01 > svn rev = 38247 > language = R > version.string = Version 2.3.1 (2006-06-01) > > Locale: > C > > Search Path: > .GlobalEnv, package:methods, package:stats, package:graphics, > package:grDevices, package:utils, package:datasets, Autoloads, > package:base > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > -- Roger D. Peng | http://www.biostat.jhsph.edu/~rpeng/ ______________________________________________ R-help@stat.math.ethz.ch 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.
