[Ifeffit] Bug in Athena?

Bruce Ravel bravel at bnl.gov
Thu Nov 19 10:48:32 CST 2009

There are a few questions all mixed together here.

Why does Athena make a merge of references?  As Matt points out, that is 
an odd thing to do.  I decided I wanted some kind of reference channel 
tied to the merged spectrum so that I could take merged data from 
different project files and figure out how to align them in a consistent 
manner.  The easiest way to do this was to tie something to the merged 
spectrum as its reference channel.  I decided to make a merge of the 
reference spectra to serve this purpose.  That was just a decision -- I 
could just as well have made a copy of the reference of the first 
spectrum in the merge list.

So what explains the behavior Darek is asking about?  Well, Athena 
doesn't actually make a serious distinction between data and its 
reference.  They are both treated normal dtaa groups internally.  The 
sense in which the reference is somehow special is that you, the user, 
tend not to look at it after you have done data alignment.

So, when you make a merge, Athena sums up all the marked groups.  Then, 
if ach one has a reference tied to it, it sums up the references and 
then ties together these two merged spectra.

However, the reference tying runs both ways.  If you change the energy 
shift for one, the other's energy shift changes the same way.  In that 
sense, there is *no* difference between data and a reference.

So, if you make a merge of data, ther references get merged into a 
merged reference.  If you make a merge of references, the data get 
merged as well.  The data groups that are maked get called "merge".  The 
merge of the tied groups gets called "  Ref merge".  If you do the merge 
of the reference channels, these two merged groups get labeled 

I think that explains everything....


On Thursday 19 November 2009 07:45:14 am Zajac, Dariusz A. wrote:
> Dear Bruce, Dear All,
> maybe it is a naïve question but I want to ask and to point this 
> Windows XP. Athena 0.8.059
> Sc.Linux. Athena 0.8.060
> I have a set of data with refernces  (one sample, many scans). I have
> marked sample's groups and do "merge marked data in mu(E)" then I get
> merged data together with reference (2 groups: merge - sample, and Ref
> merge - reference). But...
> ...if I have marked reference sample's groups and do "merge" then I 
get 2
> groups: merge - which is merged data of reference, and Ref merge - 
which is
> marged data of sample. Oposite to that I did in first example!
> Is any hidden idea, I can not see, why it should be that way? If you 
> know about that, can confuse and surprise... cheers
> darek
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 Bruce Ravel  ----------------------------------- bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Measurements Group, Beamlines X23A2, X24A, U7A

 Building 535A, Room M7
 Brookhaven National Laboratory
 Upton NY, 11973, USA

 My homepage:    http://xafs.org/BruceRavel
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