[Ifeffit] Re: Artemis Fit Questions

Scott Calvin scalvin at slc.edu
Tue Aug 17 12:16:27 CDT 2004

>Hi Dan,

>At 12:27 PM 8/16/2004 -0700, you wrote:

>>    Should I add more paths?  
>I always feel more paths are better, until the fit stops working. They will
>reduce correlations and uncertainties in general, and also reduce the
>incidence of false minima. That does mean you'll have to include some
>multiple scattering once you get far enough out, but IMHO poorly
>constrained multiple scattering is better than none at all.
>>Is there other parameters that I should add?
>>Was it Ok to make 2 separate e0's?  
>This is an ongoing debate--it cropped up again on the Ifeffit list
>recently. I am not enamored of separate E0's without a very good reason,
>but others use them more freely. On the other hand, a separate ss for the
>nearest-neighbors from paths further out (I can't tell from your
>description if there's a significant separation between the three paths) is
>often called for. You might also consider fitting a third cumulant; the
>effect on a spectrum is not unlike fitting a separate E0.
>>I think this is a pretty good fit, but I 
>>feel like there has to be something to improve it.  
>Seems not unreasonable, although it's hard to tell without uncertainties.
>That r-factor is a bit high for a three-path, five parameter fit, though.
>--Scott Calvin
>Sarah Lawrence College

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