[Ifeffit] Bug Report importing file.

Bruce Ravel bravel at bnl.gov
Mon Jul 25 08:17:22 CDT 2016


On 07/24/2016 03:55 AM, Samy Ould-Chikh wrote:
> I have some issue to import a file in Athena: just a simple x-y column (.txt attached with this email).
>
> Ti K-edge.
> Data range in the file  : 4916.30 up to 5436.88 eV.
> Issue: only data up to 5260 eV are imported (see screenshot: bug-importation).
>
> Version: Demeter 0.9.24
> System: Windows 7 Professional SP1
>
> Well, I hope it's just not me not being able to find a proper way to import the file...

I have a hard time imagining the need for an XAFS scan with 12000 data 
points.  That will usually provides a point density that about an order 
of magnitude below the core-hole lifetime, maybe 2.  In your case, it 
corresponds to about 0.04 eV steps, which seems silly to me.  While I'm 
quite open to being convinced otherwise, I cannot believe that setting 
up a scan this way is actually necessary.

But, more to the point, I think it is very unprofessional of the 
beamline staff to send you home with data in a format that is so hard to 
use.

Athena does a pretty good job of importing data in all the crazy-ass 
formats that beamlines around the world use.  But it's not really fair 
to expect that she can handle anything you can throw at her.  If a 
beamline presents data in a format that is not easy to interpret, it 
should provide tools for converting the data to a format that can 
reasonably be interpreted.

In your case, the beamline should provide you with a way to rebin the 
data either onto a more coarse grid or onto something like a 
"conventional" EXAFS grid.

So ... what I recommend, if you want to use Athena (*), is that you find 
some way to rebin your data onto a grid that fits within the 8192 limit. 
  Athena's rebinning tool uses a simple box car average -- that would 
suit your data just fine.

If you don't know what a box car average is, a google search for "box 
car average excel", "box car average matlab", "box car average python", 
etc... should provide a hint.  Once you do that, Athena should behave 
without surprises.

B

(*) Or use Athena with Larch.  Larch does not have the 8192 limit.  But 
you should still process the data onto a sensible grid.

B


-- 
  Bruce Ravel  ------------------------------------ bravel at bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 743, Room 114
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/


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