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Re: field line with NDSolve - attachment on www

• To: mathgroup at smc.vnet.net
• Subject: [mg58188] Re: field line with NDSolve - attachment on www
• From: Maxim <ab_def at prontomail.com>
• Date: Tue, 21 Jun 2005 06:03:32 -0400 (EDT)
• References: <d9397p$921$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

On Sun, 19 Jun 2005 08:09:29 +0000 (UTC), <topolog at gazeta.pl> wrote:

> Hi Daniel and All
>
> Thank you for the example - I have checked and it works. Anyway, in
> Mathematica4.0 my problem also can be solved but I moved to version
> 5.1 and here it fails. (A person from the mathgroup minded me the
> names of variables, eg. 'eqn_b', which I agree is misleading and of
> course in my code appears as 'eqnb').
>
> If I still may count on your help, on
> http://www.astri.uni.torun.pl/~krix you will find files b.mx
> (contains the whole vector b and values {xmax,ymin,ymax,zref}). and
> a notebook b.nb (prepared to work with b.mx). The link is called
> 'Temporary: MATHGROUP' (files are in an archive b.tar).
>
> I would like to remind, that the message I get (NDSolve::nlnum, see
> my previous post) is not documented yet in 5.1.
>
> Thank you and regards
> Rafal
>

If you temporarily disable $MessagePrePrint and evaluate

Block[{$MessagePrePrint},
   NDSolve[eqnbnd, r, {y, ymin, ymax}]
]

you'll see that the error message is pretty self-explanatory: it complains  
about InterpolatingFunction[{{0., 3000.}}, <>][100. + 0.*I] being  
non-numerical. You can fix this by changing the definition of b:

b = b /. InterpolatingFunction[s__] ->
   (InterpolatingFunction[s][Re[#]]&);

Then NDSolve and Plot work fine. Better yet is to investigate where the  
imaginary values in b came from.

Maxim Rytin
m.r at inbox.ru