Re: [Ifeffit] determining reasonable fitting parameters

27 Jul 2016

      That's my understanding also.
B

--
  Bruce Ravel  ------------------------------------ bravel@bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 743, Room 114
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/

On July 27, 2016, at 7:01 PM, Scott Calvin  wrote:

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  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
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Re: [Ifeffit] determining reasonable fitting parameters

Ravel, Bruce