On Mon, 10 Mar 2008, Martin Maechler wrote:
{Diverted from an R-help thread}
"Robin" == Robin Hankin <[EMAIL PROTECTED]>
on Mon, 10 Mar 2008 08:49:06 +0000 writes:
Robin> Hello Baptiste Bessel functions with complex
Robin> arguments are not supported in R.
Robin> Neither matlab nor the Gnu Scientific Library support
Robin> them either.
Robin> . . . but . . .
Robin> the pari/gp system (released on the GPL) does:
Robin> ? besselj(1+I,3)
Robin> %3 = 0.6919067491368555819808728680 + 0.4484268613977010268818252591*I
Robin> ?
Robin> You can access some pari/gp functionality from within R
Robin> by using the elliptic package, although unfortunately
Robin> its wrapper function, P.pari(), is not quite flexible enough
Robin> to deal with besselj().
Robin> I'd be happy to discuss this offline; P.pari() will need only
Robin> minor changes to accommodate besselj().
Hi Robin,
have you looked at *how* pari/gp does this?
If they have a C routine, it might be worth considering to add
``the'' complex Bessel functionality to R.
To an R package, surely? They hardly seem important enough for base R.
There are C implementations in several places, e.g. ACM algorithm 644
(also netlib.org/amos).
We have seen several occasions where people had a clear usage
need for them.
{{I have a vague déjà-vue feeling on this whole topic ....}}
Martin Maechler, ETH Zurich
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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