Re: BesselK problems at large argument?
- To: mathgroup at smc.vnet.net
- Subject: [mg78995] Re: BesselK problems at large argument?
- From: AES <siegman at stanford.edu>
- Date: Sun, 15 Jul 2007 01:07:04 -0400 (EDT)
- Organization: Stanford University
- References: <f74t6o$941$1@smc.vnet.net> <f79s6m$5ck$1@smc.vnet.net>
In article <f79s6m$5ck$1 at smc.vnet.net>,
antononcube <antononcube at gmail.com> wrote:
> These integrals are not problematic for 5.2's NIntegrate and 6.0's
> NIntegrate:
>
> In[1]:= $Version
> Out[1]= 5.2 for Linux
>
> In[2]:= Clear[expr];
> expr[n_, a_, w_] := NIntegrate[r^n*BesselK[0, w*r]^2, {r, a,
> Infinity}]
> Table[expr[1, a, w], {a, .5, 1.5, .25}, {w, .5, 1.5, .25}]
> Table[expr[3, a, w], {a, .5, 1.5, .25}, {w, .5, 1.5, .25}]
Thanks very much to you (and Bob Hanlon) for responding to my query.
Your example works fine for me also. But try changing the starting
value in the w iterator from .5 to .1 -- for me at least (using 5.2 on
Mac OS X), the integration fails with error messages such as
NIntegrate::singd
and/or
NIntegrate::inum "Integrand is not numerical at = xx`*^150"
(Sometimes one of these msgs, sometimes both. depending on choice of
parameters.)