I don't think that we need a full discussion in the Introduction, but how about early on it shows an example of 2 floating point numbers not being equal (and one of the work arounds like all.equal) along with a note (bright, bold, etc.) that says that if the reader did not expect the FALSE result then they should read FAQ 7.31 (and maybe even include a link they can click on right then).
-- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare [EMAIL PROTECTED] (801) 408-8111 > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > [EMAIL PROTECTED] > Sent: Tuesday, February 12, 2008 8:32 AM > To: [EMAIL PROTECTED] > Subject: Re: [Rd] 0.45<0.45 = TRUE (PR#10744) > > On 12-Feb-08 14:53:19, Gavin Simpson wrote: > > On Tue, 2008-02-12 at 15:35 +0100, [EMAIL PROTECTED] wrote: > >> Dear developer, > >> > >> in my version of R (2.4.0) as weel as in a more recent version > >> (2.6.0) on different computers, we found this problem : > > > > No problem in R. This is the FAQ of all FAQs (Type III SS > is probably > > up there as well). > > I'm thinking (by now quite strongly) that there is a place in > "Introduction to R" (and maybe other basic documentation) for > an account of arithmetic precision in R (and in digital > computation generally). > > A section "Arithmetic Precision in R" near the beginning > would alert people to this issue (there is nothing about it > in "Introduction to R", "R Language Definition", or "R internals"). > > Once upon a time, poeple who did arithmetic knew about this > from hands-on experience (just when do you break out of the > loop when you are dividing 1 by 3 on a sheet of paper?) -- > but now people press buttons on black boxes, and when they > find that 1/3 calculated in two "mathematically equivalent" > ways comes out with two different values, they believe that > there is a bug in the software. > > It would not occur to them, spontaneously, that the computer > is doing the right thing and that they should look in a FAQ > for an explanation of how they do not understand! > > I would be willing to contribute to such an explanation; and > probably many others would too. But I feel it should be > coordinated by people who are experts in the internals of how > R handles such things. > > Best wishes to all, > Ted. > > -------------------------------------------------------------------- > E-Mail: (Ted Harding) <[EMAIL PROTECTED]> > Fax-to-email: +44 (0)870 094 0861 > Date: 12-Feb-08 Time: 15:31:26 > ------------------------------ XFMail ------------------------------ > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
