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| Markec30 |
Posted - 06/20/2011 : 6:51:22 PM
Origin Ver. and Service Release (Select Help-->About Origin):
Operating System:
Hello;
I have got a problem with this non linear fitting which works fine in Origin 7, but in Origin 8 dose not. The program is following:
Independent variables: x
Dependent variables: y
Parameter names: a,do,d,dm
y=d*6*(1-exp(-(do*x/d)^a))^(1/a)*(1+(dm*x/d))
So this program can not be fitted till the end as in Origin 7.
Can you please help me with this problem.
Thank you in advance.
Marko
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| 1 L A T E S T R E P L I E S (Newest First) |
| Hideo Fujii |
Posted - 06/20/2011 : 7:31:03 PM
Hi,
Maybe you can follow the procedure like in this document?:
http://wiki.originlab.com/~originla/howto/index.php?title=Tutorial:User_Defined_Fitting_Function_using_OC
Please check whether the function's correctness at its Step 3.
In many cases of failure of fitting using a user defined function, the initial parameter values are not good enough in terms of the closeness to the target function. (In NLFit, you can press Chi^2 button when it starts fitting to see the current estimated curve.)
Hope this suggestion is helpful.
--Hideo Fujii
OriginLab
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