Impedance Equation fit to Complex Data

*To*: mathgroup at smc.vnet.net*Subject*: [mg86482] Impedance Equation fit to Complex Data*From*: AgustusBenjamin at gmail.com*Date*: Wed, 12 Mar 2008 00:13:46 -0500 (EST)

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

**Follow-Ups**:**Something To Dye For***From:*Daniel Lichtblau <danl@wolfram.com>