[Ifeffit] number of independent points
Kropf, Arthur Jeremy
kropf at anl.gov
Mon Oct 10 09:48:25 CDT 2011
Try it again with dk and dR extending the range.
Perhaps there is a more subtle analysis of the data range, but I doubt
it, since Matt is on record as suggesting that people not place too much
emphasis on the exact value of N-idp, if I recall correctly. You can
scale your chi-square, reduced chi-square, and errors using whatever
value of N-idp you prefer.
Jeremy
Chemical Sciences and Engineering Division
Argonne National Laboratory
Argonne, IL 60439
Ph: 630.252.9398
Fx: 630.252.9917
Email: kropf at anl.gov
From: ifeffit-bounces at millenia.cars.aps.anl.gov
[mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf Of George
Sterbinsky
Sent: Monday, October 10, 2011 9:39 AM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] number of independent points
Sorry, the log file is from Artemis, not Athena...
On Mon, Oct 10, 2011 at 10:35 AM, George Sterbinsky
<GeorgeSterbinsky at u.northwestern.edu> wrote:
Hello,
Since I haven't received a response to my previous question, I just
wanted to make sure I asked it clearly. To elaborate, I am attaching a
log from Athena. The log file lists:
"Independent points = 27.057617188"
If I attempt to reproduce this result using the equation in the feffit
document, I find
Nidp = { [2*(kmax - kmin)*(Rmax-Rmin) / pi] + 2} = { [2*(14 - 0.5)*(4.2
- 1.0) / pi] + 2} = 29.50197417,
where I have used the k-range and R-range in the log file as kmax, kmin,
Rmax, and Rmin.
Can someone explain to me why may calculation does not reproduce the
number given for "independent points" in the log fie?
Thank you,
George
On Fri, Oct 7, 2011 at 1:04 PM, George Sterbinsky
<GeorgeSterbinsky at u.northwestern.edu> wrote:
Hello,
I am wondering what values Artemis/feffit use for kmax and kmin when
calculating the number of independent points (Nidp) for a fit done in
R-space, where according the feffit document, Nidp = { [2*(kmax -
kmin)*(Rmax-Rmin) / pi] + 2}, and kmax and kmin define the fitting
range. I have tried using the Fourier transform range for kmax and kmin,
but this does not give agreement with the value of Nidp reported by
Artermis.
Thank you,
George
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