Re: Problem with evaluation of Besel Functions
- To: mathgroup at smc.vnet.net
- Subject: [mg55993] Re: Problem with evaluation of Besel Functions
- From: "David W. Cantrell" <DWCantrell at sigmaxi.org>
- Date: Wed, 13 Apr 2005 01:10:21 -0400 (EDT)
- References: <email@example.com>
- Sender: owner-wri-mathgroup at wolfram.com
Ariel sumeruk <ariel.sumeruk at gmail.com> wrote: > I am having a problem evaluating various functions, One example is the > following > > BesselJ[1.5, 0] evaluates to 0 Actually, it evaluates to 0., which is an approximate number. By contrast, BesselJ[3/2, 0] evaluates to 0 precisely. > but > (BesselJ[xx, yyy] /. xx -> 1.5) /. yyy -> 0 evaluates to complex infinity True, and that looks bad. More instructive, however, is to note that (BesselJ[xx, yyy] /. xx -> 3/2) /. yyy -> 0 evaluates to Indeterminate. Unlike ComplexInfinity, Indeterminate does not conflict with the evaluation of BesselJ[3/2, 0]. To get a numerical answer, rather than Indeterminate, we need to take a limit: In:= Limit[BesselJ[xx, yyy] /. xx -> 3/2, yyy -> 0] Out= 0 David Cantrell > 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.