Re: [Ifeffit] determining reasonable fitting parameters

2016-07-27 Thread Ravel, Bruce
That's my understanding also. B -- Bruce Ravel bra...@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:

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-27 Thread 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

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-27 Thread Neil M Schweitzer
eter: https://urldefense.proofpoint.com/v2/url?u=http-3A__bruceravel.github.io_demeter_=CwICAg=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws=oD5QfHEvBMM5YYrnfMF2YrJNX5aSKvlIRGd2B3iC9kQ=me9NMsJZQ49OCIWDVSMQ8TFLVLnHpw-OGYb2AvDyU48=WLNEeyBYvGHNsVvtMhUdPJCWK2FdLnMzBI4zMOWd9oQ=

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-27 Thread Matthew Marcus
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 - any wiggles driven in the spline will multiply the EXAFS. I haven't seen any effect from this, though. Maybe the right thing is

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-27 Thread Bruce Ravel
On 07/27/2016 04:39 PM, Matthew Marcus wrote: I'm not sure I get your point about ion-chamber response. Shouldn't that normalize out in post-edge spline? Athena edge-step normalizes (i.e. normalizes by a constant) by default. It does not do a functional (or energy dependent) normalization by

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-27 Thread Matthew Marcus
I'm not sure I get your point about ion-chamber response. Shouldn't that normalize out in post-edge spline? If the I0 chamber gets less sensitive as a function of energy, then the post-edge background rises by the same amount as the wiggles get bigger, so it divides out. Similarly for

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-21 Thread Bruce Ravel
On 07/20/2016 06:59 PM, Neil M Schweitzer wrote: In terms of the DWF’s in general, what value is considered too high? I know the DWF’s have a component that relates to temperature induced disorder in the scattering shell and a component that relates to physical disorder in the scattering shell,

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-21 Thread Bruce Ravel
On 07/20/2016 06:59 PM, Neil M Schweitzer wrote: I found a bug in the log files in the history window. I am running Demeter 0.9.21 on Windows 7. When I generate a new fit, if I change the k-range of the fit, the k-range of previous fits in the history window will also change to the current range

Re: [Ifeffit] determining reasonable fitting parameters

2016-07-20 Thread Scott Calvin
Hi Neil, This might help. It’s an abbreviated version of the discussion of criteria for judging fit quality that I later expanded on in my textbook. Northwestern doesn’t seem to have a copy of the