| T O P I C R E V I E W |
| nkourn |
Posted - 02/01/2008 : 05:36:37 AM
Origin Version (Origin Pro 7.5 SRO):
Operating System:(Windows 2000 SP4)
Hallo. I am newbie with Origin and i am facing a problem with advanced fitting tool. I want to find the fitting curve according to the equation y=100-a(1-1/e^bt) for the following data:
Time Values
0 100
10 97,52
20 64,27
30 51,69
60 49,73
I have customized the equation (as y script)The problem is that i dont know the initial a and b values in order to make the parameters initialization. So when i try t make the fit (without giving any a and b value and with automatic parameter initialization enabled) I receive the answer: "Error. The parameters a and b are not properly initialized. Check their values"
I would appreciate if you could me with this problem
Nikos |
| 1 L A T E S T R E P L I E S (Newest First) |
| easwar |
Posted - 02/01/2008 : 10:09:37 AM
Hi Nikos,
A set of initial values for all of the parameters is of course required for the iterative process to begin. With built-in functions we provide code that examines the data and comes up with initial guess values. You are working with a user-defined function, so you have two choices:
1> write some parameter initialization code, similar to what we do, to come up with values - this is beneficial if you wish to fit many datasets with this equation
2> put in some constant values - note that you can save the constant values in the fdf and if the values are "reasonable" the iterative process will converge
Easwar
OriginLab
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