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 user defined functions
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ks0297

USA
10 Posts

Posted - 10/19/2012 :  5:06:59 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi all,
y =(((2250.58*A)*x^2)/(A+B))+(0.25*B*(C/x^5)^0.25)/(A+B)

I changed my formula in to above formula, the original formula is as follows
y=TCR=(A(E/kT^2)+B(.25*c/T^5)^.25)/(A+B)
and did user defined compilation.
I am not getting the fitting results, values of A, B and C. My independent variable is TCR and dependent variable is T(=x,ie temperature)
Would some expert explain it? Thanks for help.
KS

KS

greg

USA
1378 Posts

Posted - 10/22/2012 :  09:19:13 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
The shape of your function varies wildly, depending on your parameters. Having good initial parameters thus seems crucial in order for you to fit at all. Also, due to overparamaterization, Simplex fit may be more successful than default in this case. (The S button in the fitter.)
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