This is giving you exactly what you are asking for. The operator * does element by element multiplication. So, .48 + -.48 =0, right? Is there another mathematical possibility you were expecting?
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Talbot Katz > Sent: Friday, July 27, 2007 6:31 PM > To: r-help@stat.math.ethz.ch > Subject: [R] Matrix Multiplication, Floating-Point, etc. > > Hi. > > I recently tried the following in R 2.5.1 on Windows XP: > > >ev2<-c(0.8,-0.6) > >ev1<-c(0.6,0.8) > >ev1%*%ev2 > [,1] > [1,] -2.664427e-17 > >sum(ev1*ev2) > [1] 0 > > > > (I got the same result with R 2.4.1 on a different Windows XP > machine.) > > I expect this issue is very familiar and probably has been > discussed in this forum before. Can someone please point me > to some documentation or discussion about this? Is there > some standard way to get the "correct" > answer from %*%? > > Thanks! > > -- TMK -- > 212-460-5430 home > 917-656-5351 cell > > ______________________________________________ > 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. > ______________________________________________ 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.
