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edwardclhuang
Taiwan
9 Posts |
 Posted - 05/21/2014 : 07:52:06 AM
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Origin Ver. and Service Release (Select Help-->About Origin):9.1
Operating System:Win7
Hello,
I have two sets of data y1=f1(x) and y2=f2(x). I established two non-linear curve fitting functions for each set of data with several fitting coefficients. For f1(x) the coefficients are A, t1, t2..., and for f2(x) the coefficients are A, r1, r2, and etc. The A coefficient has to be the same value for both fits and the others (t1, t2, r1, r2) are mutual independent. However, since the solutions for A are many, i.e., a lot of local minima in the solution space, the A value I get from the least-square fit on f1(x) cannot be applied to get reasonable fit on f2(x).
In a word, one needs to apply a "simultaneous" fit on f1(x) and f2(x) to get a single A value, which leads to comprised fits for two sets of data. Could you please give me some instructions about how I can do it in Origin Pro 9.1?
With best regards,
edward |
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JacquelineHe
287 Posts |
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edwardclhuang
Taiwan
9 Posts |
Posted - 05/27/2014 : 08:19:25 AM
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Dear Jacqueline,
I thank for your instruction. I do look at the example on the page "Nonlinear Multiple Variables Fitting". It shows me how to fit a single set of data by two different functions with shared parameters.
I also look at the example on the page "Global Fitting with Parameter Sharing". It shows me how to fit two sets of data by one function with shared parameter.
However, what I need is to fit two sets of data by two different functions with shared parameter. Can I do this in OriginPro 9.1 Sr1?
I thank for your help in advance,
Chien-Lung
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JacquelineHe
287 Posts |
Posted - 05/27/2014 : 10:59:57 PM
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Dear Chien-Lung,
If your two Y datasets with the same x value (XYY datasets), you can select the 3 columns and use Multiple Variables function to fit the datasets as the "Nonlinear Multiple Variables Fitting".
But if your two Y datasets with the different x value (XYXY datasets), you will need to set two functions with different "Independent Variables: x1,x2".
About how to create the User Defined Fitting Function, please refer to the simple sample in this page: http://www.originlab.com/doc/Tutorials/UserDef-FitFunc
Also, if you do not mind, you can send your project file and the fitting function formula to us, when you define the fitting function with any problem.
Tech Support department Email: tech@originlab.com
(Please send us with your detailed version and serial number information. You can check it by selecting ''Help: About Origin'' in the menu.)
Thanks
Jacqueline
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Get convergence from two Non-linear curve fittings