[Ifeffit] Re: Ifeffit Digest, Vol 5, Issue 4

Bruce Ravel ravel at phys.washington.edu
Tue Jul 8 13:59:37 CDT 2003

On Tuesday 08 July 2003 02:02 pm, Grant Bunker wrote:

> I think the easiest thing to implement in feffit however would be
> simply to do a series of minimizations with (say, 1000) random
> starting points in the parameter space. This would just entail
> wrapping the minimization in a loop, and adding a way to summarize
> the results.
> Minimizations starting at differentpoints may end up in the same or
> different "attractors". If those corresponded to bad fits, throw
> them out. If they are adequate fits, keep them. Quite possibly more
> than one attractor could fit the data adequately. A cluster analysis
> of the results should indicate whether different solutions are
> equivalent (belong to the same attractor) or not.

If Norbert or anyone else is interested in playing around with what
Grant suggests (or even one of the admitedly less-clever raster
schemes that I suggested), I have a suggestion.

One thing that Artemis will do for you is to write a script of ifeffit
commands for doing a fit using the data and feff calculation currently
imported.  See the second item in the Edit menu.  This script can be
saved to a file and used as the basis for, say, a perl or python
script to do any of the explorations of parameter space that have been
discussed today.

Here are some excellent notes from Matt explaining how to call ifeffit
from perl, python, or C:
This is exactly what Sam and I do in our programs.  And please do
report back to this list.  We'd love to know what you find!


 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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 Naval Research Laboratory                          phone: (1) 202 767 5947
 Washington DC 20375, USA                             fax: (1) 202 767 1697

 NRL Synchrotron Radiation Consortium (NRL-SRC)
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 National Synchrotron Light Source
 Brookhaven National Laboratory, Upton, NY 11973

 My homepage:    http://feff.phys.washington.edu/~ravel 
 EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/

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