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non linear regression best fit references?

TyeAldana
2-Explorer

non linear regression best fit references?

I have noisy data that I filtered using the medfilt1d smoothing function. Knowing the physics of the recorded data I know it should behave sinusoidally. If I try to do a sinfit curve fit to the filtered/or non filtered data I get a no convergence error. I have ok results using the linfit function with corr() results in the 0.85 range. I'm now looking into using the LeastSquaresFit function, and have not found much informative quicksheets or ebook examples about using this function. Can anybody provide some resources?
3 REPLIES 3

This function is included in the "Data Analysis Extension Pack" for Mathcad (example in the attachment):

"LeastSquaresFit [vx, vy, F, guess, conf, (Stdy), (LBUB), (Acc)] - Returns parameters and their confidence limits for the nonlinear fitting function F for the data vx and vy, for a confidence level conf, with optional standard deviations Stdy and optional lower and upper bounds on acceptable parameter values. Acc is the convergence accuracy."

ViktorKorobov
14-Alexandrite
(To:TyeAldana)

Example with LeastSquaresFit in Mathcad Prime 1.0.

99fb4f5745e8.jpg

Viktor

Viktor
RichardJ
19-Tanzanite
(To:TyeAldana)

If you are going to least squares fit data, do not smooth it first. It can bias the results of the fit, and will not help.

I very much doubt the LeastSquaresFit function will help either. Can you post the data?

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