Re: LegendreP & Gauss quad bug
- To: mathgroup at smc.vnet.net
- Subject: [mg25470] Re: LegendreP & Gauss quad bug
- From: Paul Cally <cally at kronos.maths.monash.edu.au>
- Date: Mon, 2 Oct 2000 22:26:51 -0400 (EDT)
- Organization: Monash University
- References: <8r1a7j$i41@smc.vnet.net> <8r6muk$t2v@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Jens-Peer Kuska wrote:
> Hi,
>
> a bug known and discussed several month ago.
>
> Regards
> Jens
>
> Paul Cally wrote:
> >
> > There is a bug in the V4 implementation of the Legendre function
> > LegendreP, at
> > least in the linux version.
> >
Thanks for this. I looked back at those notes, (from Abbott, Hanlon,
and Simons),
but no-one seemed to realize that LegendreP is simply giving the WRONG
result for Precision[x]>16.
I emailed wri about this bug. They said they would fix it for the next
version. In the
meantime, here is my temporary workaround:
legendreP[n_, m_, x_] :=
If[$VersionNumber == 4 && NumberQ[x] &&
Infinity > Precision[x] > 16, (n!)/(m!)LegendreP[n, m, x],
LegendreP[n, m, x]]
legendreP[n_,x_]:=legendreP[n,0,x]
Then use legendreP instead of LegendreP.
Paul Cally
--
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|Assoc Prof Paul Cally | Ph: +61 3 9905-4471 |
|Dept of Mathematics & Statistics | Fax: +61 3 9905-3867 |
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