Hi folks: My US$0.02 on the topic of multiple k-weight fits: There is actually value to both of the k-weighting tricks mentioned by Paul and Matt. While I agree 100% that Ifeffit and/or Artemis should include some slight of hand to manage corefinement of two or more k-weights of the same data, it is not obvious to me that a multi-k-weight co-refinement will necesarily yield the same result as the constrained parameter space mapping that Paul described. For many situations I suspect that they will, but it is easy to imagine a chi-square manifold that has many false minima deep enough to trap even a multi-k-weight co-refinement. So I think that there is still value to the procedure that Paul decribed, even in the presence of technological advancements by Matt. Indeed, I think that parameter mapping is so important that something like the procedure described in Biochemistry 35 (1996) pp. 9014-9023 (and in other articles by that crowd) is on my list of things to do in Artemis, albeit down on the list after some other stuff and not likely to appear in the next few months. ;-( As for the mechanism of how the multi-k-weight thing should be implemented -- well, I am not sold one way or the other on whether it should be a native part of the ifeffit() command or whether it should be something that Artemis in her madness should deal with. On one hand it would probably be easier for me to have Artemis generate text to do multi-k-weight as a multiple data set fit that it would be for Matt to modify the core. On the other hand, doing a multi-k-weight fit **DOES NOT** increase th amount of infomration available for the fit. Having it be a part of the ifeffit() command would guarantee that a silly user would not convince himself that the information was doubled simply by doing a k1/k3 fit. That is probably an important enough point that it suggests that ifeffit() is a better place for it. As Matt said, keep your eyes open for a new release of ifeffit and of my codes later this week. There have been some huge improvements in Artemis in the last two weeks. The next release will be a big step forward in functionality and stability. Yay! B -- Bruce Ravel ----------------------------------- ravel@phys.washington.edu Code 6134, Building 3, Room 222 Naval Research Laboratory phone: (1) 202 767 5947 Washington DC 20375, USA fax: (1) 202 767 1697 NRL Synchrotron Radiation Consortium (NRL-SRC) Beamlines X11a, X11b, X23b, X24c, U4b 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/