On 11/10/2015 05:54 PM, Carolyn Carr wrote:
Thanks so much for clarifying that for me! I have been basing my fitting in R-space off of
XAFS spectroscopy; fundamental principles and data analysis DOI 10.1023/A:1019105310221
which has a section on fitting in R-space over k-space although it is very possible I misinterpreted its analysis.
Hi Carolyn, I believe you are referring to the text at the top left of page 150 in that paper. Those authors say a number of things differently from how I would say them, however, there is one line that is certainly not relevant to how we do the analysis in Artemis and Ifeffit (or Artemis and Larch). The fitting metric in R space is evaluated using the real and imaginary parts of the complex Fourier transform. Thus, the bit at the end of that paragraph does not relate to our software. It been a long time (possibly decades!) since I have looked into the possibility of fitting magnitude and phase instead. My vague memory is that Matt found that using real/imaginary was more stable in Ifeffit. In any case, the point in that paper is not valid for our software because we use oscillatory functions when fitting in k, R, or back-transform k space. I think that helps put my earlier comment into proper context for you. Wonderful post, though! It is very pleasant to see a post that doesn't involve someone complaining about something related to the Mac! :) Cheers, B -- Bruce Ravel ------------------------------------ bravel@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/