Re: [Ifeffit] determining reasonable fitting parameters

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:

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On 07/27/2016 04:56 PM, Matthew Marcus wrote:

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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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