Dear list, I made an EXAFS analysis in Artemis (in Demeter 0.9.22) using all the available variables. This is a fragment of the .log file I got: Independent points : 17.7666016 Number of variables : 17 Chi-square : 265.0947132 Reduced chi-square : 345.8050781 R-factor : 0.0026486 Number of data sets : 1 : k-range = 2.942 - 11.043 : dk = 1 : k-window = hanning : k-weight = 1,2,3 : R-range = 1.115 - 3.5 : dR = 0.0 : R-window = hanning : fitting space = r : background function = yes : phase correction = no : background removal = E0: 20002.215, Rbkg: 1.0, range: [2.25:17.4039986832903], clamps: 0/24, kw: 2 : epsilon_k by k-weight = 3.189e-004 : epsilon_r by k-weight = 2.339e-001 : R-factor by k-weight = 1 -> 0.00220, 2 -> 0.00224, 3 -> 0.00392 The problem is that when I use the Nyquist criterion Nind=2*deltak*deltar/pi + 1 for calculating the number of independent points the value I got is much lower and close to 13. I was not aware of this discrepancy and it caused a reviewer to think I made up the fit! Am I doing something wrong? Is there another way to calculate the Nind that might have been used by Artemis? I would really appreciate any help. Yours Jesús
Jesus, On Mon, May 23, 2016 at 2:07 PM, Jesús Eduardo Vega Castillo < jevecas@gmail.com> wrote:
Dear list,
I made an EXAFS analysis in Artemis (in Demeter 0.9.22) using all the available variables. This is a fragment of the .log file I got:
Independent points : 17.7666016 Number of variables : 17 Chi-square : 265.0947132 Reduced chi-square : 345.8050781
R-factor : 0.0026486
Number of data sets : 1 : k-range = 2.942 - 11.043 : dk = 1 : k-window = hanning : k-weight = 1,2,3 : R-range = 1.115 - 3.5 : dR = 0.0 : R-window = hanning : fitting space = r : background function = yes : phase correction = no : background removal = E0: 20002.215, Rbkg: 1.0, range: [2.25:17.4039986832903], clamps: 0/24, kw: 2 : epsilon_k by k-weight = 3.189e-004 : epsilon_r by k-weight = 2.339e-001 : R-factor by k-weight = 1 -> 0.00220, 2 -> 0.00224, 3 -> 0.00392
The problem is that when I use the Nyquist criterion
Nind=2*deltak*deltar/pi + 1
for calculating the number of independent points the value I got is much lower and close to 13.
I was not aware of this discrepancy and it caused a reviewer to think I made up the fit!
Sending the entire log file is always recommended. Otherwise, you are selectively editing what you are telling us, and expecting us to guess what you haven't told us. Sending the project file is often a good choice. Fortunately, you included an important clue. You have "background function = yes", which means the fit will actually extend down to R=0, using your Rmin as Rbkg in calculating how many variables are used for the spline. With that included, the fit does contain approximately 18 independent parameters, about 5 of which will be used for the background subtraction. --Matt
Thank you once again Matt,
I am sorry for sending just a portion of the log file. I thought that way
it would be easier to look for the details. Won't happen again.
Jesús
2016-05-23 16:31 GMT-03:00 Matt Newville
Jesus,
On Mon, May 23, 2016 at 2:07 PM, Jesús Eduardo Vega Castillo < jevecas@gmail.com> wrote:
Dear list,
I made an EXAFS analysis in Artemis (in Demeter 0.9.22) using all the available variables. This is a fragment of the .log file I got:
Independent points : 17.7666016 Number of variables : 17 Chi-square : 265.0947132 Reduced chi-square : 345.8050781
R-factor : 0.0026486
Number of data sets : 1 : k-range = 2.942 - 11.043 : dk = 1 : k-window = hanning : k-weight = 1,2,3 : R-range = 1.115 - 3.5 : dR = 0.0 : R-window = hanning : fitting space = r : background function = yes : phase correction = no : background removal = E0: 20002.215, Rbkg: 1.0, range: [2.25:17.4039986832903], clamps: 0/24, kw: 2 : epsilon_k by k-weight = 3.189e-004 : epsilon_r by k-weight = 2.339e-001 : R-factor by k-weight = 1 -> 0.00220, 2 -> 0.00224, 3 -> 0.00392
The problem is that when I use the Nyquist criterion
Nind=2*deltak*deltar/pi + 1
for calculating the number of independent points the value I got is much lower and close to 13.
I was not aware of this discrepancy and it caused a reviewer to think I made up the fit!
Sending the entire log file is always recommended. Otherwise, you are selectively editing what you are telling us, and expecting us to guess what you haven't told us. Sending the project file is often a good choice.
Fortunately, you included an important clue. You have "background function = yes", which means the fit will actually extend down to R=0, using your Rmin as Rbkg in calculating how many variables are used for the spline. With that included, the fit does contain approximately 18 independent parameters, about 5 of which will be used for the background subtraction.
--Matt
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
participants (2)
-
Jesús Eduardo Vega Castillo -
Matt Newville