simultaneous fitting of multiple data sets in ifeffit
Hello! First of all I would like to thank Bruce for answering my questions. As a beginner I very much appreciate your help. Now I am trying to compare my results using two possible ways of doing EXAFS analysis : 1. Artemis 2. ifeffit command line (loading input files) Here is my question: When I use ifeffit commands it is not clear to me how to assing different kmin/kmax (rmin/rmax) values to different data sets in a multiple data set fit. My current understanding of the problem is as follows: As ifeffit documentation says all variables are global. At the same time ifeffit tries to evaluate all parameters of feffit() command first and does the fit only after determination of kmin kmax rmin rmax. What happens is that the last given values are assigned to these variables. Could somebody show me an example of a script that allows to assing different values of kmin kmax rmin and rmax for different data sets? Stanislav
Hi Stanislav,
You _can_ specify different kmin,kmax,rmin, and rmax parameters for
each data set. A simple example would be:
#---
read_data(file = my_data.chi, group=dat, type=chi)
guess(Amp= 0.9, E0= 0, dR1= 0.00)
path(1, feff= feff0001.dat, s02= Amp, e0= E0, delr= dR1)
set(kmin= 2, kmax= 12, dk= 1, rmin= 1, rmax= 3, kweight= 2)
feffit(chi= dat.chi, kmax= 10, kweight= 1, 1, data_set= 1, data_total= 2)
feffit(chi= dat.chi, kmax= 11, kmin= 3, 1, data_set= 2, data_total= 2)
#---
To address your question, this example uses both 'globally set' FT
parameters, and ones explicitly set in the feffit() command. For
the first data set, kmin, dk, rmin, rmax are taken from the 'global
parameters', while the explicit values for kmax and kweight are
used. For the second data set, kmax and kmin are explicit, and dk=
1,rmin= 1,rmax= 3, and kweight= 2, as set from the global values.
An important note is that after feffit() runs completely, the global
program variable kmax will be set to the last used value - 11.0 in
this case. This is NOT true if feffit() has data_set Hello! First of all I would like to thank Bruce for answering my questions.
As a beginner I very much appreciate your help. Now I am trying to compare my results using two possible ways of doing EXAFS
analysis :
1. Artemis
2. ifeffit command line (loading input files) Here is my question:
When I use ifeffit commands it is not clear to me how to assing different
kmin/kmax (rmin/rmax) values to different data sets in a multiple data set
fit. My current understanding of the problem is as follows:
As ifeffit documentation says all variables are global. At the same time
ifeffit tries to evaluate all parameters of feffit() command first and does
the fit only after determination of kmin kmax rmin rmax. What happens is
that the last given values are assigned to these variables. Could somebody show me an example of a script that allows to assing different
values of kmin kmax rmin and rmax for different data sets?
On Sunday 04 April 2004 09:45 pm, Stanislav Stoupin wrote:
When I use ifeffit commands it is not clear to me how to assing different kmin/kmax (rmin/rmax) values to different data sets in a multiple data set fit.
Artemis doesn't use the global variables. (Neither does Athena.) When I started writing them, it seemed that it would be easier to keep everything straight if I explicitly set kmin, kmax, etc. everytime I called feffit(), fft(), etc. And, as Matt said, Artemis is doing the typing for you. You can see how Artemis (or Athena) does its thing by looking at the ifeffit buffer, which is the second option in the Edit menu. This is a running record of every command sent to ifeffit by the program. You can also have Artemis write the ifeffit script it would use for a fit without actually running the fit. It does this specifically for people like you who might want to switch to the command line. You should be aware that Artemis moves all data and feff files into its working space, ~/.horae/stash/artemis.project.0 on unix, C:\Program Files\Ifeffit\horae\stash\artemis.project.0\ on Windows. If you use Artemis' script or cull lines from the ifeffit buffer, you will need change the paths to all files with your text editor. Good luck! B -- Bruce Ravel ----------------------------------- ravel@phys.washington.edu Code 6134, Building 3, Room 405 Naval Research Laboratory phone: (1) 202 767 2268 Washington DC 20375, USA fax: (1) 202 767 4642 NRL Synchrotron Radiation Consortium (NRL-SRC) Beamlines X11a, X11b, X23b National Synchrotron Light Source Brookhaven National Laboratory, Upton, NY 11973 My homepage: http://feff.phys.washington.edu/~ravel EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/
participants (3)
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Bruce Ravel -
Matt Newville -
Stanislav Stoupin