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 Fitting of a non linear regression plot		  New Topic  Reply to Topic
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saurabhd0911

India
4 Posts
Posted - 07/04/2016 :  01:33:49 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver.8.0 and Service Release (Select Help-->About Origin):
Operating System:Windows 10 Basic

Dear all,

I want to fit a plot using following equation:
(alpha)2/(1-alpha)=1/2KC[M]
and the plot is of alpha against M.
Can anyone please suggest me how to fit a curve with this equation. Also I want you to know that I tried putting this equation:
y2/(1-y)=1/2a*b*x
Here K is to be found and C is known. BUt I didnt get the plot correctly. Somebody please help me out with this.

Shirley_GZ

China
Posts
Posted - 07/04/2016 :  11:27:54 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Saurabhd0911,

I suppose that the equation of your fitting function is

y*2/(1-y)=1/2*a*b*x

It is an implicit fitting function which has been supported since 9.0 SR1. You can refer to this tutorial:
http://www.originlab.com/doc/Tutorials/ImplicitFit-3Var

You can download Origin 2016 SR2 demo version to have a try, http://www.originlab.com/demodownload.aspx

Thanks,
Shirley

Originlab Technical Service Team
Edited by - Shirley_GZ on 07/04/2016 11:28:36 PM
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saurabhd0911

India
4 Posts
Posted - 07/05/2016 :  05:16:29 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
I tried following the instructions as given in the tutorial site by going through Samples>curve fitting> but I cannot see Implicit.Dat file. Can you please help me out here.

Thank you.
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Shirley_GZ

China
Posts
Posted - 07/05/2016 :  06:08:28 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Do you mean the sample data "Ellipsoid.dat"? It is shipped with Origin, but not included in Origin 8.0.

If you want to follow the tutorial, the required minimum Origin version is Origin 9.0 SR1, just as the note in the Summary section.

Thanks,
Shirley

Originlab Technical Service Team
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saurabhd0911

India
4 Posts
Posted - 07/06/2016 :  08:17:17 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Yes, I mean ellipsoid.dat file.

However, I tried fitting another simplified equation

alpha= (1+8KCM)^1/2-1/4KCM
as y= (1+8*a*b*x)^1/2-1/4*a*b*x

However, this time I got the exact parameters whereas earlier this was not the case. But it says error 207 Fitting not proper. Can you suggest me a way out of it?
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Shirley_GZ

China
Posts
Posted - 07/07/2016 :  01:03:44 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

The details of the Fit Status code are here,
http://www.originlab.com/doc/Origin-Help/NLFit-Result-FitStatusCode

According to the error message, you are suggested to check the initial values and parameter constraints firstly. If still problem, please send us the project file(with fitting results) and the *.FDF file you defined via tech@originlab.com.

Please provide the serial number of your Origin in your email. We need it to record your question in our problem tracking base.

Thanks,
Shirley



Originlab Technical Service Team
Edited by - Shirley_GZ on 07/07/2016 01:06:53 AM
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