Re: Gauss2DFit question

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

"Kenneth P. Bowman" <kbowman@null.net> writes:

> [[ This message was both posted and mailed: see
>    the "To," "Cc," and "Newsgroups" headers for details. ]]
> 
> In article <on3dnrl7o9.fsf@cow.physics.wisc.edu>, Craig Markwardt
> <craigmnet@cow.physics.wisc.edu> wrote:
> 
> > http://cow.physics.wisc.edu/~craigm/idl/idl.html
> 
> Thanks, Craig.  I greatly appreciate the help.
> 
> I was thinking of writing a GAUSS2DFIT replacement using the built-in
> Levenberg-Marquardt algorithm, LMFIT.  Have you compared the built-in
> function with your LM algorithm?  (For speed, accuracy, etc.?)

I haven't done any direct comparisons, but I would expect any better.
In the speed category it will definitely be a loser, since it does a
function call for *each* data point.  For images that's a lot of
points!

MPFIT is based on MINPACK-1 which which was designed to handle more
difficult problems.  I believe that LMFIT is descends from Numerical
Recipes which doesn't have that reputation.

Craig

P.S.  MPFIT is not the end-all, be-all.  It fails this problem
miserably, <http://www.maxthis.com/curviex.htm>, but I believe this is
because the initial trial function spans about 8 orders of magnitude.

-- 
--------------------------------------------------------------------------
Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
--------------------------------------------------------------------------