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rainbowkoala
29 Posts |
 Posted - 03/29/2014 : 04:05:04 AM
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Origin Ver. and Service Release (Select Help-->About Origin): OriginPro 8.5.0 SR1
Operating System: win7
Hello,
I hope you can help me with the following problem:
The equation is given as follows.
y = y1 + i * y2 = A/[ 1 + (ixt)^a ]
I only have :
colA = x (independent variable)
ColB = y2 (dependent variable)
If I have ColC = y1 (dependent variable), I could fit the data with the complex function. But this one is beyond my capability.
Any help.....?
Thanks for your help.
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SeanMao
China
288 Posts |
Posted - 03/31/2014 : 06:08:29 AM
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Hi,
It is possible if all the fitting parameters are independent.
We can use Non-Linear fiting (NLfit) tool to fit only the imaginary part to obtain parameter A, t, a. To do that, first you need to create a new fitting function in the “Fitting Function Builder” dialog. Select “Tools:Fitting Function Builder” menu and the dialog box will be brought up. Please follow these steps to define the fitting function:
1. Click “Next” to create a new function.
2. Input function name and choose “Function Type” as Origin C. Click “Next”.
3. Input Independent Variables as “x”, Dependent Variables as “y”, Prameter names as “A0,t,a”. Click “Next”.
4. Paste the following codes into “Function Body” box:
complex f=A0/(1+(1i*x*t)^a);
y=f.m_im;
To make sure our define function is correct, you have to click on the Origin C editor icon on the top right corner of “Function Body” box to compile it. Click on the “Compile” and close “Code Builder” dialog.
Click “Finish” to save the fitting function and close the dialog.
Then you can use the defined fitting function to do non-linear fitting.,
Select “Analysis:Fitting:Nonlinear Curve Fit:Open dialog” menu to bring up the NLFit dialog box. In the “Function Selection” part, choose “User Defined” in “Category” drop-down list, and choose the function you defined under“Function” list as shown in figure below:
More details about NLfit tool can be found through the link below:
http://www.originlab.com/doc/Tutorials/Fitting-NLFit-Basic
Regards!
Sean
OriginLab Technical Services |
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Fitting only with imaginary coefficient