Thomas, Thank you for your response. I checked the FAQ and it provides an example using sqrt(2) where you'd expect numerical precision to be an issue.
I guess that I expect R to act pretty much as C or C++ would do if I were to program the same code. It's a bit of a surprise that assignment of rationals, well within precision, followed by multiplication leading to a result well within precision picks up those extra bits along the way. Something to watch out for, to be sure. Thanks again for your help Paul >From: Thomas Lumley <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >CC: r-devel@stat.math.ethz.ch, [EMAIL PROTECTED] >Subject: Re: [Rd] bug? (PR#8074) >Date: Tue, 16 Aug 2005 16:06:48 -0700 (PDT) > >On Wed, 17 Aug 2005 [EMAIL PROTECTED] wrote: >>I just don't understand this: >> >>>(2*2)==4 >>[1] TRUE >>>.2*.2 >>[1] 0.04 >>>(.2*.2)==.04 >>[1] FALSE > >It's a FAQ, not a bug. Consider: > >>(.2*.2) - .04 >[1] 6.938894e-18 > >and read the FAQ > > -thomas > > >>or >> >>>x=.04 >>>x >>[1] 0.04 >>>y=.2*.2 >>>y >>[1] 0.04 >>>y==x >>[1] FALSE >> >>______________________________________________ >>R-devel@r-project.org mailing list >>https://stat.ethz.ch/mailman/listinfo/r-devel >> > >Thomas Lumley Assoc. Professor, Biostatistics >[EMAIL PROTECTED] University of Washington, Seattle ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
