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@anl.gov

From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@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@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@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