[Ifeffit] Plotting chi(k) linear combination fit in energy

Tue Jul 21 00:32:23 CDT 2015

Ellen,

In the LCF tool, after you do the fit in chi, select norm in the "fitting space" radio button and click the "Plot data and sum" button. It will plot the current fit's weightings. You can also type in the weighting you would like to plot, if you already have a table of results.

After doing this, you can use the "Make group from fit" button to add it to your project (but you can't transform it like a regular data file, as you noticed, so you might want to write both the xanes and the chi), or you can export it using the "Save fit as column data" button. Those buttons seem to write the plotted data, so make sure you have first plotted what you want to export.

Leslie

**
Leslie L. Baker, Ph.D.
Research Assistant Professor
Department of Geological Sciences and
Department of Plant, Soil and Entomological Sciences
University of Idaho
875 Perimeter Drive MS 2339
Moscow, ID 83844-2339
208-885-9239
http://scholar.google.com/citations?user=ejpH5p0AAAAJ

________________________________
From: ifeffit-bounces at millenia.cars.aps.anl.gov <ifeffit-bounces at millenia.cars.aps.anl.gov> on behalf of Ellen Daugherty <daughertyee at gmail.com>
Sent: Monday, July 20, 2015 7:09 PM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Plotting chi(k) linear combination fit in energy

Sorry that I did not explain that clearly. Matt Newville's interpretation is correct.

Ellen

On Jul 20, 2015, at 19:41, Matt Newville <newville at cars.uchicago.edu<mailto:newville at cars.uchicago.edu>> wrote:

I think Ellen wants to first do a linear combination fit with chi(k) data and then look at what that combination of spectral components  would look like for the XANES region.  It seems like a fine idea to me.

Off the top of my head I don't know the easiest way to do this.  I don't think there is a single button for that, but I've been known to miss hidden features in Athena for years.

--Matt

On Jul 20, 2015 8:16 PM, "Scott Calvin" <scalvin at sarahlawrence.edu<mailto:scalvin at sarahlawrence.edu>> wrote:
Hi Ellen,

Either I'm not understanding what you're trying to do, or what you're trying to do doesn't make sense.

XANES is generally plotted as mu(E) or norm(E). To get from norm(E) to chi(k), two things must be done: a smooth background must be subtracted from norm(E), and E has to be converted to k. The conversion from E to k is reversible, but the background subtraction is not, since chi(k) is meant to be background independent. You therefore cannot, in principle, plot chi(k) data as norm(E).

-Scott Calvin
Sarah Lawrence College

On Jul 20, 2015, at 7:48 PM, Ellen Daugherty <ellen.daugherty at colostate.edu<mailto:ellen.daugherty at colostate.edu>> wrote:

Hello,

I was unable to find an example of this question in the archive, but please let me know if it has already been addressed. I would like to plot the results of linear combination fits performed in chi(k) in energy space to compare them to XANES fits. When I try to plot the saved fit in energy, I get a message saying: "chi data cannot be plotted in energy." Is there any way to do this other than to use Excel to scale the weights of the standards? This would be exhausting to perform for combinatorial fits. I am using Athena in Demeter 0.9.20 on Windows 7. I have attached a sample and a few standards for aid in addressing the issue.

Thank you!

Ellen

--
Ph.D. Candidate
Research Assistant, Borch Lab<http://borch.agsci.colostate.edu/>
Department of Chemistry
Colorado State University
http://borch.agsci.colostate.edu/group-members/ellen-daugherty/
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