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MathGroup Archive 2005

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Re: Re: RootSearch-missing root

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62346] Re: [mg62252] Re: RootSearch-missing root
  • From: <bsyehuda at gmail.com>
  • Date: Mon, 21 Nov 2005 03:54:38 -0500 (EST)
  • References: <dlen7g$8d1$1@smc.vnet.net> <200511172203.RAA16296@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

RootSearch is not a Mathematica function in version 5.2 as well
yehuda

On 11/18/05, dh <dh at metrohm.ch> wrote:
>
> Hi Ania,
> RootSearch is not a Mathematica function (at least not in version 5.0).
>
> Further, with question like this you should give a sample input.
>
> However, there is a package RootSearch from the author:
> ted.ersek at navy.navy.mil
>
> This package is numerical! No numerical routine can garantee (for a
> general function)that it can find all the roots. Every numerical routine
> must sample some interval and can miss. To see this, simply consider a
> function of a real argument that is positive everywhere and dips below
> zero only on a very short interval.
> The best you can do is to increase the number of sample points.
>
> sincerely, Daniel
>
> nastazjaf wrote:
> > Hello,
> > I have a problem with the RootSearch. I have searched the archive and
> > the RootSearch Examples and couldn't find an answer or at least the
> > similar problem. The RootSearch doesn't find one of the roots. There ar=
e
> > three roots, all three are clearly resolved when two functions are
> > plotted but RootSearch finds only two of them. I tried to play with the
> > options and with different values of xmax and xmin, and it just doesn't
> > see it. FindRoot finds the missing root for well defined starting
> > values. But I need to have all three roots. In what circumstances the
> > RootSearch cannot find one of the roots?
> >
> > Thanks
> > Ania
> >
>
>


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