MathGroup Archive 2005

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

Search the Archive

Legendre Polynomials

> BesselJ[1.5, 0] evaluates to 0 but
> (BesselJ[xx, yyy] /. xx -> 1.5) /. yyy -> 0 evaluates to complex infinity
> I seem to encounter many of these problems with Bessel and Legendre
> functions where I get actual diffrent numerical results depending on
> How I set the parameters.

I worked with Legendre Polynomils and also experienced the problem. If
you use
LegendreP[60, 1.] you have the correct answer 1. It looks like it uses
a smart algorythm. If you use LegendreP[60, x] /. x -> 1. mathematica
first finds the explicit forms of the polynomail, and only afer that
puts x->1. which means that you have to sum up tirms of odre say 10^20
to get 1. Due ti rounding errors you may obtain a wrong answer.

  • Prev by Date: Re: Mandrake 10.1 and Mathematica 5.0?
  • Next by Date: Re (correction): confusion about Thread[]
  • Previous by thread: Re: Mandrake 10.1 and Mathematica 5.0?
  • Next by thread: Re: Legendre Polynomials