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 Nonlinear curve fitting with multiple variable		  New Topic  Reply to Topic
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Showmik

Korea
6 Posts
Posted - 07/02/2019 :  01:23:31 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
OriginPro 8 SR4, v8.0951(B951)
Operating System: Windows 7

Hello,

I want to generate a correlation between multiple variables using the nonlinear curve fitting. I want to use the formula y=C*x1^a*x2^b. Here, x1 and x2 are the independent variables and y is the dependent variable. How can I create such a user-defined function and use the relevant experimental data for generating the equation? In this case, the parameters would be a, b and C. I have experimental data for y, x1, and x2.
Any kind of help would be highly appreciated. thanks

Showmik

AmandaLu

439 Posts
Posted - 07/02/2019 :  03:34:21 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

Please refer to this tutorial:

https://www.originlab.com/doc/Tutorials/UserDef-FitFunc

Thanks,
Amanda
OriginLab Technical Service
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Showmik

Korea
6 Posts
Posted - 07/02/2019 :  04:03:54 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks for the tutorial. I checked it but my problem is while fitting with multiple variables. The tutorial shows only 1 dependent and 1 independent variable and how to use it. In my case, I need to find the correlation with 1 dependent and 2 independent variables. Hope you understand the situation

Showmik
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Chris D

428 Posts
Posted - 07/02/2019 :  09:33:27 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
you can actually create your own fitting function that accepts multiple independent variables.

Here is a tutorial:
https://www.originlab.com/doc/Tutorials/Fitting-MultiIndepVar

And here are the docs about creating a user defined fitting function:
https://www.originlab.com/doc/Tutorials/UserDef-FitFunc

Creating a user-defined fitting function isn't "click-click" easy-peasy, but they are not particularly hard to do either if you follow the steps.

I hope this helps!

Thanks,
Chris Drozdowski
Originlab Technical Support
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Showmik

Korea
6 Posts
Posted - 07/03/2019 :  10:30:59 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks for the help. I was able to perform the nonlinear fitting by my own user-defined function.

Showmik
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