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 problem in Non linear curve fitting		  New Topic  Reply to Topic
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Abbas1206

Pakistan
1 Posts
Posted - 06/22/2018 :  01:40:15 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hellow
i am new to origin and need help regarding nonlinear curve fitting for user defined function. The model equation i am following is:

((P1*1.602e-19*P2)/(1+(P2*x)^2) +P3/(1+(P4*x)^2)+P5/(1+(P6*x)^2))/
(((P1*1.602e-19*P2)/(1+(P2*x)^2) +P3/(1+(P4*x)^2)+P5/(1+(P6*x)^2))^2 +
((P1*1.602e-19*P2)*P2*x/(1+(P2*x)^2) +P3*P4*x/(1+(P4*x)^2)+P5*P6*x/(1+(P6*x)^2))^2)

P1,P2,P3,P4,P5,P6 are parameters i want to calculate. In model this equation fitt well but i face problem that peaks are ignored during fitting (equation cannot fit peaks).

Model:

My Fitting:

Thanks in advance

Abbas

Shirley_GZ

China
Posts
Posted - 06/22/2018 :  06:14:58 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Abbas,

In general, if the fitting results are not as good as you expected, we will suggest you to check if the initial values of parameters are improper.
You can estimate a group of initial values and then validate them by simulating curves with the fitting function(to make sure there are peaks with these initial values).

Thanks,
Shirley
OriginLab



Originlab Technical Service Team
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