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NonlinearFit. Range not working ?

  • To: mathgroup at
  • Subject: [mg21220] NonlinearFit. Range not working ?
  • From: Axel Kowald <axel at>
  • Date: Mon, 20 Dec 1999 02:27:42 -0500 (EST)
  • Organization: None
  • Sender: owner-wri-mathgroup at


I'm using NonlinearFit (actually NonlinearRegress) to fit a function to
some data. Some of my parameters must not fall below zero, so I
specified my parameters as {symbol, start, min, max} with min being
zero. However, although the documentation says "the search for the
parameters terminates if the search goes outside the specified range"
this isn't true for me :-(
It does try negative values and because this leads to a negative log in
my function it gives nasty error messages.
This behaviour seems also to depend on the Method used. All except
Gradient show this behaviour. However, when using Gradient a message
from FindMinimum appears saying that it has reached a point outside the
range and then stops, without giving any result !

Has anyone experienced something like this before ?  What am I doing
wrong ? Is there an (easy) alternative to NonlinearFit ?

Many thanks,

P.S. I'm using NT4 & Mathematice 4


Dr. Axel Kowald                                  Email:
a.kowald at
Humboldt University Berlin                       Tel:   +49 30 20939105
Innovationskolleg Theoretische Biologie          Fax:   +49 30 20938801
Invalidenstr. 43
10115 Berlin


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