[Ifeffit] merging I0

Bruce Ravel ravel at phys.washington.edu
Wed Jul 2 16:55:43 CDT 2003

Hi folks,

As Matt suggested, I will take a stab at this question.

> > I had a question I was hoping you could help me with.  I have imported a
> > bunch of ASCII type files into Athena and averaged them all together.  The
> > ASCII files contain the Energy, detector file, I0, I1, and I2.  After I
> > average the files together, I want to save the file and export it as an
> > ASCII file.  I understand how to do this, but when I do it I only obtain
> > the Energy, [detector/IO], and background in column three (like it states
> > in the manual).  Now what I want to do, is extract the averaged I0 column
> > from the process.  Is there anyway to do this or will I just have to
> > average I0 in another software.  Any help with this would be appreciated.

> I believe you'd have to average all the I0 values yourself, and that
> athena cannot do this easily.  Bruce might correct me on this....  
> It would be possible to do this using the Ifeffit commands directly
> (including in the athena command window), something like this:

Matt's suggeted sequence of raw ifeffit commands is certainly a fine
way of doing what Jacob asked for.  Averaging I0 alone is not
something I had in mind when I designed Athena's basic interface
features, but it should be possible.

As is the case when one tries to explain a sequence of mouse clicks,
this will be rather wordy.  Sorry....

As all Athena users know, the first thing that happens when you import
a data file is to interact with the file selection dialog:
Athena remembers which columns were used to make the numerator and
denominator of the expression that constructs mu(E) from the column
data.  (Note that the ability to make detector groups is lost once the
data are saved to a project file.  Making detector groups is something
that must be done during the session in which the raw data are

In the Group menu is a option for "Make detector groups".  This will
make entries in the Data groups list for the numerator and denominator
used to make the original data group.

So my solution to Jacob's problem was to import data files one-by-one.
Each time, I made the detector groups.  Once all the data was imported
and the detector groups were made, I marked the denominator groups (my
test data were all transmission, so I0 was in the denominator).  Then,
in principle, one could select "Merge marked data in mu(E)" from the
Merge menu and have the merged I0 data that Jacob was looking for.

*In principle*.  In fact, there is a bug in the current version of
Athena and the merge of the I0 data failed.  That bug will, however,
be fixed soon.  Once that is done, it will be possible, albeit
inconvenient, to merge I0 data as Jacob wants.  You may wish to try
working through the procedure that I described to understand how the
detector group feature of Athena works, even if the final step will
fail in the current version.


P.S. I am pretty certain that this will be fixed in time for the next
release of Athena and that the next release will be before Friday the

 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)
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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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