Hi all, A project we're working on now seems like something that shouldn't be that hard to do in Artemis, but it's proving unwieldly. I was hoping someone could suggest a less cumbersome method: We have data on 11 related samples, plus a standard. All use the same FEFF calculation and paths (about 25 paths or so). Each one was analyzed as a separate project file, and gave us promising results. Now we would like to perform a multiple-data set fit...on all the samples if possible, or some subset if not. There are a couple of reasons for wanting to do this. One is to get a more robust determination of parameters that are universal to all samples, like S02, rather than just depending on the fit from the standard. The other is that one parameter we are fitting (crystallite size) quite properly shows a rather large uncertainty in its fit. But it is clear from playing around that the difference between samples for crystallite size is much better determined. Our plan is to guess crystallite size for one particular sample, and guess a difference from this size for each of the other samples. This should, of course, not yield a significantly different result from just guessing each size. But then we'd like to set the crystallite size for the first sample to its best-fit value. The only purpose for this is to obtain an estimate of the uncertainty in the =relative= crystallite sizes of the samples. OK, so that's the plan, but the implementation is awkward. It seems to me that with the current version of Artemis we have to pretend that there is a separate FEFF calculation for each sample, and we have to enter all the path parameters anew for each sample. There's a lot of nitty-gritty constraints on multiple-scattering paths and such, so that's a lot of data entry. Also, I forget what the current limits are on total number of FEFF paths and total number of samples--are we going to be hitting limits? Basically, I can understand if we simply can't fit this many samples simultaneously with the standard code. That's not a big problem; we can get most of what we want by fitting a subset of the samples. It's the data-entry that's a bit of a pain. For each sample we have to re-enter all of the path and GDS information, and I think we'll get a bloated ZIP file, since presumably the FEFF calculation will be repeated once for each sample even though they are all identical. This doesn't seem like all that unusual a scenario. Does anyone have a good idea of how this should be done in Artemis, or do we just have to bite the bullet and re-enter all the pertinent information for each sample we bring in (and live with the bloated project file). --Scott Calvin Sarah Lawrence College P.S. Thanks to Matt and Bruce again for even making such a thing conceivable. The analysis on this project is being done by a talented freshman without coding experience. It is a tribute to the software (and the student!) that we've been able to get so far so fast.