This is a bug in the mingw runtime, and not in R. So the difference is
between OSes, not between R versions. Note that
> acosh(2)
[1] 1.316958> acosh(2+0i)
[1] 0+NaNi> acosh(2+1e-10i)
[1] 1.316958+0i
so it seems to be happening only for exactly real complex numbers.
I think there are also problems with branch cuts.
On Thu, 30 Nov 2006, tshort at eprisolutions.com wrote:
> Full_Name: Tom Short
> Version: 2.4.0
> OS: Windows XP
> Submission from: (NULL) (68.236.159.227)
>
>
> It looks like there's a bug in acosh with complex number in windows:
>
>> acosh(2)
> [1] 1.316958
>> acosh(2+0i)
> [1] 0+NaNi
>
> This happens for me on Windows XP with the following versions:
> R version 2.2.0, 2005-10-06, i386-pc-mingw32
> R version 2.4.0 (2006-10-03) i386-pc-mingw32
>
> It works fine with the following:
> R version 2.4.0 (2006-10-03) i386-pc-linux-gnu (debian)
> R version 2.1.0, 2005-04-18, i386-pc-linux-gnu (debian)
>
>> acosh(2+0i)
> [1] 1.316958+0i
>
> I didn't find any problem with asinh or atanh taking complex numbers.
In
> src/main/complex.c, there are some #ifdef Win32's in z_asin and z_acos,
so it
> may be related to that.
acosh is unrelated to those.
> - Tom
>
> Tom Short
> EPRI Solutions, Inc.
>
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>
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
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