From: Brian Gough <bjg@network-theory.co.uk>
To: Andreas Gros <agros@rz.uni-osnabrueck.de>
Cc: gsl-discuss@sources.redhat.com
Subject: Re: Nonlinear Least Squares Fitting
Date: Fri, 16 Nov 2001 14:39:00 -0000 [thread overview]
Message-ID: <15354.8667.540079.973847@debian> (raw)
Message-ID: <20011116143900.Z9Ec_HoP47BK7nhz99e1Ih28ZAjEXNgLOvp2ArJhzFE@z> (raw)
In-Reply-To: <200111200858.fAK8w4f10486@omecihuatl.rz.uni-osnabrueck.de>
Andreas Gros writes:
> In the section "Providing the function to be minimized" where the
> function gsl_multifit_function_fdf is described, you mention the
> function f that should store the distance between the values
> calculated by the algorithm and the provided values. As I tested
> the algorithm I've found, that this distance is not taken as a
> "square", instead the algebraic sign of the distance seems to be of
> some importance. My results were quite different, whenever I took
> (y[i]-Yi) instead of (Yi-y[i]) (as it is shown in the example).
> Taking the latter the solver works fine, taking the first distance
> the results have been quite funny.
Hi,
The sign of the jacobian needs to match the sign of the function.
If you change one you need to change the other.
I think this will fix your problem.
regards
Brian
next prev parent reply other threads:[~2001-11-20 10:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-19 13:20 Andreas Gros
2001-11-16 10:53 ` Andreas Gros
2001-12-19 13:20 ` Brian Gough [this message]
2001-11-16 14:39 ` Brian Gough
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