Hi Matt, Thanks for your detailed instructions. I am just trying to follow the steps and see how it works. I am not trying to do complicated things. My issue is I would expect the grey vertical lines after press the "Fit Baseline" button, but nothing shows up. I tried to select a larger region(which was not pre-peak), also nothing happened. So I am confused. Besides, can I use the XAS Viewer to do main peak fitting? I know that Larch has its own language based on python. I am wondering can I use larch function, like fitting peaks in Jupiter Notebook? Thanks for your help.
Thank, Xinyue On Sat, May 2, 2020 at 6:36 AM Matt Newville <newvi...@cars.uchicago.edu> wrote: > Hi Xinyue, > > On Fri, May 1, 2020 at 9:16 PM Xinyue Wang <xyw0...@gmail.com> wrote: > >> Hi, >> >> I am Xinyue, a student who interested in using XAS Viewer. My issue is >> when I tried baseline fitting, I followed the document. But there was no >> region, no centroid, and no fitting line shown. Here is a screenshot of my >> work. Could you please help me with this? >> Thanks for your help. >> > > It's hard to tell from the screenshot alone. Just to clarify, the idea > for the panel is to fit pre-edge peaks to known lineshapes (Gaussian, > Lorentzian, Voigt, etc). The interface could probably be used for > general-purpose curve-fitting of many kinds of spectra, but right now it > definitely skews to pre-edge peak fitting. > > Because of that emphasis, the idea is to first press the "Fit Baseline" > button -- this will do a crude fit of a Lorentzian + Line that are meant to > represent any residual background and the main absorption edge. The fit > for this baseline is done over the energy range defined by "Fit Energy > Range" but ignoring the "Pre-edge Peak Range", which is meant to be the > portion of the XAS spectra where the pre-edge peaks are. That is, this > baseline fit should > look something like Figure 5.4.2 at > https://xraypy.github.io/xraylarch/xasviewer/index.html#pre-edge-peak-fitting. > In that figure, the black dots show the ends of the Pre-edge Peak Range > that is ignored in this baseline fit. For sure, the initial guess for > this range may not be very good. But it is easy to refine this ignored > range. It is also not actually critical to get this baseline fit perfect - > it's just a place to start the fits of the peaks themselves, and the > remaining fits will refine the baseline as well as the peaks over the full > energy range. After a baseline fit is done, you can add peaks and then > use the "Fit Model", which fits over the whole "Fit Energy Range", > ignoring the "Pre-edge Peak Range". > > From your screenshot, I don't see much of a pre-edge and not many obvious > peaks. The result is that the actual fit energy range for the baseline > (that is > "Fit Energy Range" - "Pre-edge Peak Range") is very short. I can believe > the fit will fail under those conditions. But I sort of think that failure > really comes because your data doesn't have pre-edge peaks. > > Maybe you are trying to do something more complicated? > > --Matt > > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit >
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