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Topic: Curve fitting - retrieve original values after centering and scaling
Replies: 4   Last Post: Jul 30, 2013 12:19 PM

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Michael Ranftelhuber

Posts: 4
Registered: 12/10/12
Curve fitting - retrieve original values after centering and scaling
Posted: Jul 15, 2013 11:44 AM
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Hi,

I have a problem with the curve fitting toolbox. I want to fit a curve through measured dispersion points of a fiber to get the higher orders of dispersion. The dispersion is generalliy defined as:

D(w) = beta1 + beta2(x) + beta3./2.*(x^2) + ...

where beta1, beta2, beta3, ... are the values I want. Looks like a simple polynomial to me. However when I put the data into cftool and make a fit it warns me: "Equation is badly conditioned. Remove repeated data points or try centering and scaling".

But scaling obviously changes the fitting parameters, which is what I want. How can I rescale the system in order to get the "real" beta1, ... values from the scaled polynomial coefficients p1, p2, ...?

This is really a huge problem for me atm!

Thanks!



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