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MRI_aic
1 Posts |
 Posted - 10/01/2012 : 12:14:37 PM
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I am trying to fit two dependent curves like:
y = exp(-(a+b)*x) & z = b/d*exp(-a*x)*(1-exp(-d*x))
with parameters a,b & d but I have the following error message:
(11) Parameter Initialization was called.
(12) ----------Levenberg-Marquardt-----------
Reduced Chi-sqr = --
Iterations Performed = 0
Total Iterations in Session = 0
(13) Fit did not converge - zero or missing weight value is not allowed for chosen weight method.
Anybody any idea?
Thanks! |
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Hideo Fujii
USA
1582 Posts |
Posted - 10/01/2012 : 4:18:43 PM
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Hi MRI_aic,
I suspect that the initial values of the parameters, a, b and d are not close enough to lead the convergence, though not sure.
Maybe first you can try to define one-dependent-variable function separately, and make sure each works? Once they work surely, then you can come to the two-dependent-variable function.
--Hideo Fujii
OriginLab |
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easwar
USA
1964 Posts |
Posted - 10/01/2012 : 5:32:56 PM
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Hi,
Looks like you have assigned Weights during fitting, and the data has zero or missing values.
Weighting methods such as Instrumental assign reciprocal weights such as 1/value^2, so if any of the values are 0 or very close to zero, or missing, fitting cannot proceed.
Easwar
OriginLab |
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two dependent curve fitting