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From: Karl Ratzsch <mail.kfr@gmx.net>
Newsgroups: comp.graphics.apps.gnuplot
Subject: Re: What's new in gnuplot 5.2
Date: Fri, 2 Jun 2017 10:18:37 +0200
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Am 01.06.2017 um 08:16 schrieb hugocoolens@gmail.com:
> Is it possible to put in an easy way constraints on the fitting parameters in this version of Gnuplot? I've always missed something like being able to put in "0<a<10" for a function fit with a as a parameter?

Unfortunately not, but for some good reason.

It's not a simple thing to add constraints to the Marquardt-Levenberg
algorithm, because it's not clear (and probably very problem-dependent)
what should happen when the parameter approaches that limit. You
probably know the feature from "OriginPro", and most people i know agree
that it messes up their fitting routines quite a bit.

Most often when one parameter wants to diverge, that is because the
given function does not really describe the data or the starting values
are bad. Trying to predetermine them by fitting only certain parts of
your data using simplified functions is usually helpful.

  Karl