Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: LegendreP error (bug?) in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81214] Re: LegendreP error (bug?) in Mathematica
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Sun, 16 Sep 2007 04:02:15 -0400 (EDT)

On 9/15/07 at 4:15 AM, rschmied at gmail.com (Roman) wrote:

>But, instead of telling you that you are getting garbage, the
>algorithm returns a number with exaggerated precision:

>In[3] := LegendreP[200, 43, 0.8] // Precision
>Out[3] = MachinePrecision

As I understand the documentation, expressions with only exact
numbers and machine precision numbers always return
MachinePrecision as the precision. If I have this correct, then
Precision only returns useful results when expressions make use
of Mathematica's variable precision arithmetic.

Instead of Precision using Accuracy

In[5]:= LegendreP[200, 43, 0.8] // Accuracy

Out[5]= -102.834

gives a clear indication what is returned by LegendreP[200, 43,
0.8] is problematic.

--
To reply via email subtract one hundred and four


  • Prev by Date: Re: Previous version features for 2-D and 3-D plots
  • Next by Date: Re: Re: rationalize numerator of quotient
  • Previous by thread: Re: Re: LegendreP error (bug?) in Mathematica
  • Next by thread: Re: Re: LegendreP error (bug?) in Mathematica