Fitting with a complex equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg18403] Fitting with a complex equation*From*: "Gibum Kim" <gibumk at tamu.edu>*Date*: Wed, 7 Jul 1999 00:11:03 -0400*Organization*: Texas A&M University, College Station, Texas*Sender*: owner-wri-mathgroup at wolfram.com

Hi, there. I'm having a trouble with the determining parameters of the equation with the experimental data. This is my equation. f(x)=Abs[A/(wa-x-I Ga)+k E^(I t)]^2 A,wa,Ga,k and t are parameters I want to find. I know the best guess of the parameters. Even with the best guess values, I got totally wrong values of them using "FindMinimum". Here's the program I got from mathematica support. ClearAll[A,wa,Ga,k,t] data=ReadList ["onepeak.dat", Number, RecordLists-> True] f=Abs[A/(wa + x - I Ga) + k E^(I t)]^2 <<Statistics` model[A_?NumberQ,wa_?NumberQ,Ga_?NumberQ, k_?NumberQ,t_?NumberQ,x_?NumberQ]:= Abs[A/(wa + x - I Ga) + k E^(I t)]^2 sse[A_,wa_,Ga_,k_,t_]= Plus @@ Apply[(model[A,wa,Ga,k,t,#1]-#2)^2 &, data,{1}]; FindMinimum[sse[A,wa,Ga,k,t], {A,8.1,8.5},{wa,2958,2962},{Ga,8.2,8.6}, {k,0.3,0.4},{t,32,35},MaxIterations->500] Do you have any idea? Your any suggestion would be grateful.