I am writing to make you aware of what I believe to be a bug in (D)Athena. To demonstrate the problem, I have attached a project file containing two groups. Both groups have the same energy range but were measured with slightly different point spacings. Attempting to merge the two groups results in Athena excluding one of the groups from the merge "for being too short." Thank you, George
George, It seems rather unconventional to try and merge data which has different energy grid spacing? I thought the main point of merging data is to reduce the noise and uncertainty of a measurement. I am not sure how the exact method of merging data is implemented but I don't think it is fair to call this a bug as a result of a unique situation. Could you or have you reinterpolate one spectrum? Chris Patridge ******************************** Christopher J. Patridge, PhD NRC Post Doctoral Research Associate Naval Research Laboratory Washington, DC 20375 Cell: 315-529-0501 On 2/26/2013 6:55 PM, George Sterbinsky wrote:
I am writing to make you aware of what I believe to be a bug in (D)Athena. To demonstrate the problem, I have attached a project file containing two groups. Both groups have the same energy range but were measured with slightly different point spacings. Attempting to merge the two groups results in Athena excluding one of the groups from the merge "for being too short."
Thank you, George
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Hi Chris,
The reason that I have spectra with different point spacings is because I
felt that a given range of the spectrum was oversampled. That is to say,
all of the spectral features could be captured with less points. It is not
clear to me why merging two spectra, where one has more data points than
necessary, would not still reduce the noise and uncertainty of the
measurement. Could you elaborate on your concern?
Thank you,
George
On Wed, Feb 27, 2013 at 8:24 AM, Christopher Patridge
George,
It seems rather unconventional to try and merge data which has different energy grid spacing? I thought the main point of merging data is to reduce the noise and uncertainty of a measurement. I am not sure how the exact method of merging data is implemented but I don't think it is fair to call this a bug as a result of a unique situation. Could you or have you reinterpolate one spectrum?
Chris Patridge
******************************** Christopher J. Patridge, PhD NRC Post Doctoral Research Associate Naval Research Laboratory Washington, DC 20375 Cell: 315-529-0501
On 2/26/2013 6:55 PM, George Sterbinsky wrote:
I am writing to make you aware of what I believe to be a bug in (D)Athena. To demonstrate the problem, I have attached a project file containing two groups. Both groups have the same energy range but were measured with slightly different point spacings. Attempting to merge the two groups results in Athena excluding one of the groups from the merge "for being too short."
Thank you, George
_______________________________________________ Ifeffit mailing listIfeffit@millenia.cars.aps.anl.govhttp://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
On Wednesday, February 27, 2013 11:09:17 AM George Sterbinsky wrote:
The reason that I have spectra with different point spacings is because I felt that a given range of the spectrum was oversampled.
You could reverse the order of the data sets in the list (Alt-j/Alt-k). Then the densely sampled data would be interpolated onto the grid of the sparser data, which you assert is adequate. Interpolating onto a sparser grid is much less worrisome than interpolating onto a denser grid. Given that Athena has no way of evaluating whether the grid density is appropriate to the measured spectrum (that is, Athena has no way of knowing that the one data set was in fact oversampled), Athena is justified in fretting when you ask it to do something that poses a genuine threat of damaging the data. (Admitedly, this threeat is only to the merged spectrum in this case, not to any of the original data.) By default, Athena wants not to damage your data. That behavior can be turned off, as I showed in the screenshot in my last post. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel
On Tuesday, February 26, 2013 06:55:21 PM George Sterbinsky wrote:
I am writing to make you aware of what I believe to be a bug in (D)Athena. To demonstrate the problem, I have attached a project file containing two groups. Both groups have the same energy range but were measured with slightly different point spacings. Attempting to merge the two groups results in Athena excluding one of the groups from the merge "for being too short."
Look at the merge preferences. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel
Thanks Bruce
On Wed, Feb 27, 2013 at 8:28 AM, Bruce Ravel
On Tuesday, February 26, 2013 06:55:21 PM George Sterbinsky wrote:
I am writing to make you aware of what I believe to be a bug in (D)Athena. To demonstrate the problem, I have attached a project file containing two groups. Both groups have the same energy range but were measured with slightly different point spacings. Attempting to merge the two groups results in Athena excluding one of the groups from the merge "for being too short."
Look at the merge preferences.
B
--
Bruce Ravel ------------------------------------ bravel@bnl.gov
National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973
Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Dear all, I am following Bruce’s video presentation on the Artemis case of FeS2, and have a beginner’s question here. There is a configuration of S1 ---- Fe ---- S2 . In order to use the existing sigma^2 defined for single scattering path of [Fe – S], Bruce applied linear combination for the following paths: Fe ---- S1 ---- S2 ---- Fe Sigma^2 of this path = sigma^2 [Fe – S] *2 Fe ---- S1 ---- Fe ---- S2 ---- Fe Sigma^2 of this path = sigma^2[Fe – S) *2 Fe ---- S1---- Fe ---- S1 ---- Fe Sigma^2 of this path = sigma^2 [Fe – S] *4 Hence the question is, why the third path multiplies 4 while the other two paths multiply 2? For me they should all be 2. Thanks. Regards, Zhipeng
On Thursday, February 28, 2013 01:33:41 PM pmzl@leeds.ac.uk wrote:
Hence the question is, why the third path multiplies 4 while the other two paths multiply 2? For me they should all be 2.
Go to http://bruceravel.github.com/XAS-Education/ Scroll down to "Recommended reading". Follow the link to Eric Hudson's paper. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel
participants (4)
-
Bruce Ravel -
Christopher Patridge -
George Sterbinsky -
pmzl＠leeds.ac.uk