It's called `rounding error'. Please look it up in an introductory numerical analysis textbook. Please also read the section on `what is a bug' in the R FAQ, and if you do report a genuine bug please try to use an informative subject line.
On Fri, 5 Apr 2002 feng@tu-cottbus.de wrote:
Full_Name: Jinsheng Feng Version: R141 OS: Linux and Windows2000 Submission from: (NULL) (141.43.226.235) I have installed R141 under Xteamlinux4.0 (Chinese) and MS Windows2000. By run following I have two resalts: A <- matrix(c(1, 2, 7, 3), ncol=2, byrow=T) Ai <- solve(A) b <- c(2, 3) x <- Ai%*%b resalt under Windows
x
[,1] [1,] -2.220446e-16 [2,] 1.000000e-00 resalt under Linux
x
[,1] [1,] 1.110223e-16 [2,] 1.000000e-00 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
Brian D. Ripley, ripley@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._