Nonliear Fit

*To*: MathGroup at yoda.physics.unc.edu*Subject*: Nonliear Fit*From*: Michael Buschmann <mike at mem.unibe.ch>*Date*: Mon, 10 Jan 94 15:49:06 +0100

I'm trying to fit the magnitude of a nonlinear complex function of real variables to real data. I am using the NonlinearFit routine in the Statistics standard package directory (John Novak Feb 1992) When I am able to find an real analytic expression for the magnitude of the complex function, the routine works fine. When I simply place The Abs[] operator around the complex function, no fitting is done and the initial values are returned. When I use an interpolation function to represent the magnitude of the complex function I get a 'dmval' error message that the input value lies outside the domain of the interpolation function, even though it does not. I would like to get the fit working without having to always find an analytic expression for the magnitude of the complex function. Either using the Abs[] operator or an interpolation. Any ideas ? Mike Buschmann