| T O P I C R E V I E W |
| studentAgain |
Posted - 07/07/2014 : 5:20:20 PM
Origin Ver. and Service Release (Select Help-->About Origin):
Operating System: OriginPro 8.1 SR3, Windows 8.1
Hello,
I have a quick question about the nonlinear curve fitting. When I try to fit my data with for instance, Polynomial cubic function
y = A + B*x + C*x^2 + D*x^3
everything works great when I use automatic parameter initialization, however; as soon as I try to change slightly any of the parameters manually (i.e by typing its value in the parameter box) the fit becomes poor and does not converge any more. I click "fit until converged" button but nothing happens (it shows a message: "cannot find direction to change parameters to reduce Chi-sqr"), the parameter that I just manually entered appears to be frozen/fixed and does not change anymore. I do not understand why and would really appreciate any help.
Thank you,
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| 2 L A T E S T R E P L I E S (Newest First) |
| studentAgain |
Posted - 07/10/2014 : 5:27:12 PM
Thank you for your reply. I've sent the data and more detailed description of the problem to the above address. Looking forward to your reply! |
| Shirley_GZ |
Posted - 07/07/2014 : 11:22:55 PM
Hi,
I can't reproduce the problem, please send us sample data and tell us the details to help us reproduce the problem here.
Via: tech@originlab.com
Shirley
Originlab Technical Service Team |
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