| T O P I C R E V I E W |
| ZY4914 |
Posted - 04/09/2014 : 4:13:13 PM
Origin Ver. and Service Release (Select Help-->About Origin): 9.1
Operating System:Window 8.1
Hi, I need help to create a non-linear curve fitting function for the following expression:
y = C + A/3*(x^2*(3-x^2/B)/(1-x^2/B))-(x-x^3)*(3-1/(x*B))/(1-1/(x*B))
where C, A, and B are positive constants I would like to get.
I have tried creating the function by inputting the above formula and setting x as independent variable, y dependent variable, C, A, and B as parameters greater than 0. However, the resulting fitting was not successful.
Thank you in advance for your comments and suggestions.
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| 3 L A T E S T R E P L I E S (Newest First) |
| ZY4914 |
Posted - 04/10/2014 : 2:00:54 PM
Fitting can be done after setting appropriate initial values for the parameter, but very time-consuming.
I have deleted my reply with sample data set and curve.
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| ZY4914 |
Posted - 04/10/2014 : 11:21:56 AM
Hi Zahraa,
The function that I intended to use for fitting my data is an empirical expression reported by others in my filed. I am interested in exacting the constants A and B from my data. |
| zahraa |
Posted - 04/10/2014 : 11:06:28 AM
Hi ZY4914,
Is there a specific reason you wish to use that function and not a different one? Just asking since an exponential function would fit your sample data completely, there are many built in exponential functions in Origin that worked when I tried it. |
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