Re: fitting, step

  John,

I am using isis 1.6.0-19. I was mistakenly referring to mpfit as lmdif. 
But all the tests I reported with lmdif were actually done with mpfit, 
since that's the default fit method.

Maurice

On 7/7/10 8:03 PM, John Houck wrote:
> On Wed, Jul 07, 2010 at 19:46 -0400, Maurice Leutenegger wrote:
>>   Mike, Dave, John,
>>
>> thanks for your suggestions. I tried changing the fit method to subplex,
>> and it was able to fit correctly. But lmdif doesn't work at all. So for
>> now I will use subplex for my fitting, but let's continue to work on
>> getting lmdif to work as well, because there's no reason it shouldn't.
> For what it's worth, lmdif was recently removed from isis
> (as of isis-1.5.0-28) and replaced with mpfit.
>
> This was done primarily because mpfit has better support for
> enforcing bound constraints on fit parameters. With lmdif, isis
> enforced bound constraints using a crude hack that sometimes
> failed in the way that you're seeing -- the optimizer failing
> to move away from the initial parameter values.
>
> What version of isis are you using?
>
> Thanks,
> -John

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