On Fri, Sep 13, 2024 at 1:10 PM Duncan Murdoch wrote: > [You don't often get email from murdoch.dun...@gmail.com. Learn why this is > important at https://aka.ms/LearnAboutSenderIdentification ]
> Caution: External email. > On 2024-09-13 8:53 a.m., Jonathan Dushoff wrote: > >> Message: 4 > >> Date: Thu, 12 Sep 2024 11:21:02 -0400 > >> From: Duncan Murdoch > >> That's not the correct formula, is it? I think the result should be x * > >> Conj(y) / Mod(y)^2 . > > Correct, sorry. And thanks. > >> So that would involve * and > >> / , not just real arithmetic. > > Not an expert, but I don't see it. Conj and Mod seem to be numerically > > straightforward real-like operations. We do those, and then multiply > > one complex number by one real quotient. > Are you sure? We aren't dealing with real numbers and complex numbers > here, we're dealing with those sets extended with infinities and other > weird things. Definitely not sure, just thought I would suggest it as a possibility. > So for example if y is some kind of infinite complex number, then 1/y > should come out to zero, and if x is finite, the final result of x/y > should be zero. > But if we evaluate x/y as (x / Mod(y)^2) * Conj(y), won't we get a NaN > from zero times infinity? Yes, and it's not trivial to work around, so probably not worth it. Thanks, ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
