Re: Impedance Equation fit to Complex Data

*To*: mathgroup at smc.vnet.net*Subject*: [mg86499] Re: Impedance Equation fit to Complex Data*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Wed, 12 Mar 2008 05:27:48 -0500 (EST)*Organization*: Uni Leipzig*References*: <fr7opm$39a$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, FindFit[] cant handle complex values ? as the error message "The function value {-0.658637+7.38957\ I,0.0321006+5.39846\ \ I,<<8>>,<<3>>} is not a list of real number" say ? Regards Jens AgustusBenjamin at gmail.com wrote: > Dear Group, > > I'm trying to fit an equation to data using FindFit. When I type > in the equation and data and then FindFit, I get this: > > Z := [Omega]^(-(2 ArcTan[H/G])/[Pi]) (G - i H) + R > > Data := {{1.`, 2.658637`- 8.389573` i}, {1.5`, > 1.784396`- 6.214955` i}, {2.5`, > 1.656569`- 3.97147` i}, {3.5`, > 1.633799`- 2.878841` i}, {5.5`, > 1.357069`- 1.776964` i}, {6.5`, > 1.259121`- 1.848249` i}, {8.5`, > 1.105417`- 1.344566` i}, {9.5`, > 1.119456`- 1.148945` i}, {11.5`, > 1.082122`- 1.064767` i}, {14.5`, > 1.015714`- 0.8684088` i}, {15.5`, > 1.055329`- 0.664562` i}, {18.5`, > 0.8675349`- 0.5107938` i}, {20.5`, > 0.8968949`- 0.4148388` i}} > > FindFit[Data, Z, {R, G, H}, \[Omega]] > > FindFit::nrlnum: The function value {-0.658637+7.38957 \ > \[ImaginaryI],0.0321006+5.39846 \[ImaginaryI],-0.0241135+3.33901 \ > \[ImaginaryI],<<5>>,0.212762+0.769883 \[ImaginaryI],0.246899+0.605796 > \ > \[ImaginaryI],<<3>>} is not a list of real numbers with dimensions \ > {13} at {R,G,H} = {1.,1.,1.}. >> > > Why?!?!? Why can't FindFit handle this? What's wrong with it not > being a list of real numbers? I'm pulling my hair out. I've looked > at others' suggestions for similar problems and they don't work for > this problem. Am I out of my mind? Does anyone have a suggeston? > > Regards, > > Benji >