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 Global fitting two curves with different functions		  New Topic  Reply to Topic
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wmm265

USA
2 Posts
Posted - 04/26/2018 :  12:53:20 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi,

I'm trying to globally fit my data (two curves) to obtain shared parameters using two different user-defined equations.

They are:

y=R2a+rex*(1-(((4*x)/kex)*tanh(kex/(4*x))))

and

y=R2b +1.78*rex*(1-(((4*x)/kex)*tanh(kex/(4*x))))

In the equations I float rex, kex, and R2a/b. Each equation fits one curve.

I'm not sure how to do this in origin. Any help would be appreciated

arstern

USA
237 Posts
Posted - 04/26/2018 :  2:14:29 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

Please see if this tutorial is helpful:
https://www.originlab.com/doc/Tutorials/Multi-Functions-Global-Fitting

Thanks,
Aviel
OriginLab
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wmm265

USA
2 Posts
Posted - 04/26/2018 :  4:37:58 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Aviel,

Thanks for the link. It was helpful. It looks like this is really good if you have only two y-columns to fit. In this example it was L1 and L2. What if you had many more like L1-L100, and you only wanted to fit two columns at a time (i.e L3 and L4, then L5 and L6) instead of fitting one parameter for all of the data?

William
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arstern

USA
237 Posts
Posted - 04/27/2018 :  12:23:19 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi William,

To conduct nonlinear fitting on specific columns, you will want to select your X column and Two Y columns in the worksheet i.e. L3 and L4 then Select Analysis -> nonlinear curve fitting ....

To select specific columns in the worksheet -> Select your first column then hold the CTRL button as you select your other columns.

-Aviel
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