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 ______________________________________________ [email protected] 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.
