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Hideo Fujii
USA
1582 Posts |
 Posted - 07/29/2011 : 2:14:34 PM
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Hi Malte,
You can set the lower and upper bounds for parameters you want in NLFit fitting tool by the following:
1) In NLFit, choose "Bounds" tab, double-click the cell of "LB" (or "UB") for the parameter; Each double-clicking cyclically change between empty, "<=" and "<". Choose either "<=" or "<".
2) Double-click the cell of "LB Value" (or "UB Value"), and enter the lower (or upper) parameter value such as 0.6 for A.
3) Make sure that the values of all parameters are filled (i.e. non the missing value "--"). If you still have "--" for some parameters, fill their initial estimates (a middle value between lower- and upper bounds).
4) You can check the current goodness of parameters visually by pressing Chi^2 button. If the curve is good enough, you can run fitting by pressing "Fit until converged" button.
Hope the above explanation is helpful.
--Hideo Fujii
OriginLab
P.S. You cannot use [...] in the definition of your user-defined function, and you have to use (...), instead. Therefore, you can define, say by Fitting Function Organizer (or Fitting Function Builder in ver. 8.5.1).
y = A - B * (1 - exp(-C * sqrt(x))) |
Edited by - Hideo Fujii on 07/29/2011 5:03:19 PM |
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Problem with own fit
