Re: RootSearch-missing root
- To: mathgroup at smc.vnet.net
- Subject: [mg62252] Re: RootSearch-missing root
- From: dh <dh at metrohm.ch>
- Date: Thu, 17 Nov 2005 17:03:47 -0500 (EST)
- References: <firstname.lastname@example.org>
- Sender: owner-wri-mathgroup at wolfram.com
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.
> 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 are
> 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?
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