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T O P I C    R E V I E W
Semipolar Posted - 07/25/2011 : 05:35:49 AM
Is there anybody who can help me?I would like to do curve fitting by using this equation,I=a((e^(b*V))-1)+c((e(d*V))-1)
I have shown the following I-V graph of a paper relation with this fitting equation. I would like to fit just like that fitting. But, I could not solve the fitting problem. In that paper, where a,b,c and d are the coefficients.
The values of the parameters of the I-V Graph are(a=-1.1x10-15A, b=-2.6V-1 ) (c=5.2x10-21A, , d=25.9V-1 ).
here is my data,
V I
0 -9.222E-10
0.025 -5.319E-10
0.05 -1.488E-10
0.075 2.242E-10
0.1 5.853E-10
0.125 9.969E-10
0.15 1.4703E-9
0.175 1.8115E-9
0.2 2.1769E-9
0.225 2.5617E-9
0.25 3.0249E-9
0.275 3.4178E-9
0.3 3.9538E-9
0.325 4.7053E-9
0.35 5.5561E-9
0.375 6.4127E-9
0.4 7.3102E-9
0.425 8.1442E-9
0.45 9.11579E-9
0.475 1.01499E-8
0.5 1.12095E-8
0.525 1.24289E-8
0.55 1.36778E-8
0.575 1.4883E-8
0.6 1.61328E-8
0.625 1.76907E-8
0.65 1.92396E-8
0.675 2.08109E-8
0.7 2.25632E-8
0.725 2.43765E-8
0.75 2.62425E-8
0.775 2.83771E-8
0.8 3.04131E-8
0.825 3.26391E-8
0.85 3.49362E-8
0.875 3.74592E-8
0.9 3.9961E-8
0.925 4.2853E-8
0.95 4.56726E-8
0.975 4.87165E-8
1 5.18794E-8
2   L A T E S T    R E P L I E S    (Newest First)
Semipolar Posted - 07/26/2011 : 8:55:41 PM
Hi Fujii,

Iput the parameters of a,b,c,d are 1. But I could not solve the problem. I don’t know over-parameterized or not.Could you give me further instruction?
I really appreciate your help.
Hideo Fujii Posted - 07/25/2011 : 11:32:00 AM
Hi Semipolar,

Maybe you can first try the following tutorial ("Help: Tutorials" menu) at the following section for the fitting with a user defined function:

Tutorials> Fitting> User Defined Fitting Function using OriginC

Here, you can see a example how to define a user-defined function, and fit the data with the defined function. Then, you can define your function with I as a dependent variable, V as an independent variable, and a, b, c and d as parameters.

Hope this helps.

--Hideo Fujii
OriginLab


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