RobustFit is a free utility programme for robust locally-weighted scatterplot smoothing (Lowess), or robustly fitting data to a polynomial function.
Lowess Smoothing
A standard way of smoothing data to reduce noise is to apply a moving average (MA) filter. The MA filter works by replacing each data point by the average of itself and a number of data points within a user-determined window on either side of the point in question.
Robust polynomial fitting does not use a moving window, but fits the entire data set to a polynomial function, without any location-specific weighting
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