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

[Bruce Ravel]

Leslie had a good suggestion.  That would, I think, be close to what you 
want.

There is not a button to automate exactly what you want -- not even one 
that I've been hiding from Matt all these years.

Another way of doing what you want would be to jot down the best fit 
values for the weights, then use the data summation tool 
(http://bruceravel.github.io/demeter/aug/process/sum.html) to make that 
sum of norm(E) spectra.  These is no automated interaction between these 
tools, so you'll have to do the tedious work of setting things up in the 
summation tool.

Another idea would be to jot down the best fit value, then mark the data 
group and the groups used as the fitting standards, then select "Save 
marked groups as ... norm(E)" from the File menu.  Import that file into 
Excel or whatever and use the weights you jotted down.  Again, there is 
no automation to do this.

That said, "plot this result in norm(E) for a fit in chi(k)" is a good 
and useful idea.  I'll put it on my to do list.

B


On 07/20/2015 10:09 PM, Ellen Daugherty wrote:
> 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/
>>>     <Sample.nor><Standard 1.nor><Standard 2.nor><Standard
>>>     3.nor>_______________________________________________
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-- 
  Bruce Ravel  ------------------------------------ bravel at bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 535A
  Upton NY, 11973

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