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 Can not fit Hill Equation when n =-1		  New Topic  Reply to Topic
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mklab2

USA
1 Posts
Posted - 05/04/2013 :  12:54:23 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
I am trying to fit Hill equation

y=Vmax X^n/((K^n+X^n))

when n is >0, it is fitting fine,

but when n = -1 , or some number < 0, it can not fit. It shows:

"Fit did not converge - mutual dependency exists between parameters.
You may have overparameterized the fitting function. Fixing one of them may eliminate this problem."

and give me a horizontal line
Please help me , what is the problem with the fitting ? ( I did not change anything with the function)

Sam Fang

291 Posts
Posted - 05/06/2013 :  11:07:06 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Origin's built-in Hill function has a constraint by default:
n > 0


You can remove the constraint if n<0 in NLFit dialog's Bounds tab as shown below.



Sam
OriginLab Technical Services
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