[Ifeffit] determining reasonable fitting parameters

[Scott Calvin]

This is also related to whether it is appropriate to apply a McMaster correction to sigma2 after fitting, right? (Or “during,” but since it’s just an offset, it amounts to the same thing.) In Bruce’s method, a McMaster correction is appropriate, although often it’s small in comparison with the reported uncertainties anyway. In Matthew’s method, there is no need for a McMaster correction. Essentially McMaster attempts to correct for using a constant normalization instead of the expected smooth decrease in the normalization factor after the edge. Or am I remembering the meaning of that correction wrong?

—Scott Calvin
Sarah Lawrence College

> On Jul 27, 2016, at 5:26 PM, Matthew Marcus <mamarcus at lbl.gov> wrote:
> 
> I think that if the wiggliness in the spline is enough to cause trouble by the mulriplicative effect, then it's probably eating up the wiggles by subtraction, anyway.
> However, I can see that you wouldn't want the bother and potential for trouble involved in having a second curve for the post-edge division.
> 	mam
> 
> On 7/27/2016 2:08 PM, Bruce Ravel wrote:
>> On 07/27/2016 04:56 PM, Matthew Marcus wrote:
>>> Oh, so it assumes that chi(k) = (mu(E(k))-spline(k))/const.?  Mine does
>>> (mu(E(k))-spline(k))/spline(k), which I guess has its own problems
>> 
>> Exactly.  Both solutions have problems.  The potential for trouble with "/const" seems less severe to me and easier to support (in the sense of supporting the use of a software package).  So that's why Athena does what she does.
>> 
>> B
>> 
>> 
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit