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, ...?