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Re: LevenbergMarquardt

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  • Subject: [mg86598] Re: LevenbergMarquardt
  • From: Bill Rowe <readnews at>
  • Date: Fri, 14 Mar 2008 04:18:34 -0500 (EST)

On 3/13/08 at 4:33 AM, ausman at (Ausman, Kevin) wrote:

>Here is what I am trying to do:


>The problem is that without specifying LevenbergMarquardt as the
>method I get an error that the gradient is effectively zero, but
>when I do specify Levenberg Marquardt it says that my function isn't
>of the appropriate form:


>The parameters for residFunc are some experimental data and some
>fitting paramters (typically in lists), and it returns a
>one-dimensional list of numbers.

This last comment suggest you want to do a least squares fit of
data to a specified model. While it should be possible to do
this with FindMinimum, why not use FindFit? FindFit is
specifically designed to solve a least squares problem while
FindMinimum is a more general tool. As a general rule of thumb,
tools more specifically designed for a given problem in
Mathematica will outperform more general tools for that problem.

Like FindMinimum, the default method for FindFit is Automatic.
However, I believe FindFit tries Levenberg-Marquardt first with
this setting since that will generally produce better results
for a non-linear least squares problem.

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