[Ifeffit] spline clamps in ifeffit code

Bruce Ravel bravel at bnl.gov
Mon Dec 14 12:42:44 CST 2009

On Monday 07 December 2009 05:37:41 am you wrote:
> Hi Bruce,
> I have a question concerning the spline clamps in ifeffit. Is there
> any possibility to set them directly in the spline() command? I tried
> to do it with spline(..., clamp1=0, clamp2=24,...) but it did not work
> and by default both spline clamps seem to be zero. Unfortunately I
> found nothing about it in the reference guide either. So how can I
> configure the clamps in the Ifeffit code?
> Thanks and kind regards,

Hi Jan,

I am CCing this to the Ifeffit mailing list, which is the better place
to ask a question of this sort.  I was out of town all of last week --
had you sent this to the mailing list rather than to me directly, you
probably would already have received an answer.

You seem to have the syntax correct.  That is, if you follow along in
Athena's Ifeffit buffer, you see that "spline(..., clamp1=0,
clamp2=24,...)" is exactly what she does.  Anything you see in the
Ifeffit buffer should be directly transplantable to an Ifeffit
script.  Indeed, that is the very purpose of making the Ifeffit buffer
available to the user.

So, what do you mean that the clamps both seem to be zero?  How do you
know that?  Can you show us an example data file and a short example
ifeffit script that demonstrates the problem?  It is quite possible
that changing the clamp strength will have no significant impact of
the background removal.  To refresh my memory as I am writing this
email, I loaded an iron foil spectrum into Athena.  Indeed, changing
clamp 2 has little impact on the background removal.  But I know from
experience that, in general, it does.

Just to tell the whole story, I'll point out that the numeric values
of the clamp strengths in Athena are configurable.  If you go to Edit
preferences, then open the clamp group, you will be able to assign new
values to the 5 named clamp strengths.



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

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

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