[Ifeffit] Find R-factor for linear combination sums?

[Bruce Ravel]

On Saturday, January 07, 2012, 01:42:43 pm, Scott Calvin wrote:

> Hi all,
> 
> Is there a way to get Athena (or Ifeffit) to report an R-factor for a
> linear combination sum, as opposed to a fit? Artemis does that for FEFF
> fitting, and Athena will do a linear combination sum ("plot data + sum"
> with weights entered into the LCF standards boxes), but I don't see a way
> to get it to report the statistics.
> 
> Here's the reason I'd like to be able to do this: when I run LCF fits, I
> often do one fit for XANES and another on chi(k) for EXAFS (and perhaps
> another using the derivative of XANES, just for good measure). The fits
> unsurprisingly usually give somewhat different weights to each fraction.
> So suppose XANES tells me my sample is 0.22 A and 0.78 B, and EXAFS tells
> me its 0.28 A and 0.72 B. I'd like to be able to force the EXAFS to 0.22 A
> and 0.78 B (i.e. the results of the XANES fit), and have it give me an
> R-factor for that sum. Then I could apply something like a Hamilton test
> to decide if they're actually consistent.
> 
> If it's not currently a feature, it's one I'd like to see. It's not that
> high a priority--I can just export the spectra and calculate it in Excel.
> But it would be nice.


That's a reasonable request.  I'll put it on the to do list for the new 
version of Athena.

B

 

-- 
 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/