On Tue, 3 Jul 2007, matt wrote: > I have the following data for a lossy material (nylon), and I'd like to > find the parameters for meep's lorentzian model which fit the data: > > frequency (hz) real(eps) imag(eps) > 60 3.7 -.0666 > 1e3 3.5 -.0651 > 1e6 3.14 -.068452 > 1e8 3.0 -.06 > 3e9 2.84 -.033228 > 2.5e10 2.73 -.028665 > > There was an indication in a previous post that this is simple: > >> G.J. Parker >> original patch posted by Steven, this does reduce memory requirements when >> using Lorentzians. i have no problems using five Lorentzians w/ this patch. >> one can write a stupid excel spread sheet to fit N lorentzians to a table of >> (experimental) complex epsilons...
I'm not sure it's quite so simple, because most off-the-shelf fitting programs only fit a real-valued function, whereas here you have to fit a complex-valued function. In general, you have to use a nonlinear optimization program to do the fit (to minimize the sum-of-squares errors or whatever error criterion you prefer). I don't have any off-the-shelf code to do this for the Lorentzian problem (although of course there are lots of off-the-shelf nonlinear optimization routines), but perhaps someone on the list does. Steven _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
