ARE: [Ifeffit] Re: Ifeffit Digest, Vol 5, Issue 1

Bruce Ravel ravel at phys.washington.edu
Mon Jul 7 12:11:08 CDT 2003


On Monday 07 July 2003 12:45 pm, Matt Newville wrote:
> Anyway, I think using the 'epsilon_k' that chi_noise() estimates as
> the noise in chi(k) is a fine way to do a weighted averages of data.
> It's not perfect, but neither is anything else.

Exactly right!  As Matt explained, there are reasons to believe that
the measurement uncertainty is dominated by things that Parsival's
theorem doesn't address and that measuring those problems is hard.

As Matt said, weighting by 1/chi_noise() is OK.  As Scott said,
weighting uniformly is OK.  Those are two choices are the most OK I
can think of, so Athena will let you choose between them.

While I am of the chorus of people agreeing with Grant that mu is not
equal to <If>/<I0>, I can see no reason why Athena should actively
prevent the user from looking at <If> or <I0>, if that is what he
wants to do.  The *current* version of Athena prevents this, but
that's a bug not a feature! ;-)

B



-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
 Code 6134, Building 3, Room 222
 Naval Research Laboratory                          phone: (1) 202 767 5947
 Washington DC 20375, USA                             fax: (1) 202 767 1697

 NRL Synchrotron Radiation Consortium (NRL-SRC)
 Beamlines X11a, X11b, X23b, X24c, U4b
 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/



More information about the Ifeffit mailing list