[Ifeffit] Minor bugs in the new versions

Bruce Ravel ravel at phys.washington.edu
Wed Apr 28 10:05:21 CDT 2004

On Wednesday 28 April 2004 05:20 am, Schmithals wrote:
> I made a mistake in my previous posting:
> athenatest.zip contains two experimental files: exp01.dat and exp02.dat
> with a (slightly) different scaling. I read them in and exported to
> exp01.xmu and exp02.xmu. The values indeed correspond exactly to the
> original files.
> But if I import both groups to a single file then the scaling of the
> first group will be used for both and the ordinate data from exp02 will
> be changed accordingly. How is this done, linear interpolation?

Aha!  I misunderstood the question.  You are refering to the energy
grid on which the data are written out.  I had thought that by
"scaling" you were refering somehow to the height along the y-axis.

Yes -- when Athena exports many data groups in one file, it selects
the energy grid of the first marked group (i.e. the one occupying the
top-most position in the group list) as the standard and then
interpolates each of the other groups onto that energy grid using
Ifeffit qinterp() function.  This interpolation is necessary for a
file with a single energy column.

FYI, Athena also interpolates when doing a merge and in any other
situation where a common energy grid is called for.

> Actually, I find this behaviour very useful: if I export many groups for
> display in an other program I can plot all of them versus the same
> abzissae-values. Is it possible to integrate that feature for export of
> single files as well? (as I now prefer that method because of the
> automatic parameter export).

Sort of.  It is possible to interpolate data as it is imported to the
energy grid of the standard using the pre-processing feature of the
column selection dialog.  However any kind of e0 shift, either by
calibration or alignment, would undo that.

Athena should allow you to interpolate a group onto the grid of
another group at any time.  I'll put that on the to do list.


 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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 Naval Research Laboratory                          phone: (1) 202 767 2268
 Washington DC 20375, USA                             fax: (1) 202 767 4642

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