Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
(801) 408-8111
> -----Original Message-----
> From: r-devel-bounces at r-project.org
> [mailto:r-devel-bounces at r-project.org] On Behalf Of
> Ted.Harding at manchester.ac.uk
> Sent: Tuesday, February 12, 2008 8:32 AM
> To: r-devel at stat.math.ethz.ch
> 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, labonne at st-pee.inra.fr 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) <Ted.Harding at manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 12-Feb-08 Time: 15:31:26
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