We're using the Theil-Sen estimator for fitting a line (orange) through mostly straight data. It works very well compared to the linear trendline (blue) in Excel:
We also need to fit mostly curved data with outliers. Is there something similar to the Theil-Sen estimator we could use? Excel's second degree polynomial trendline (blue) for all points, results in a bad fit due to the outliers on the right. When the data is manually truncated to 0 < x < 1.9, the polynomial trendline (orange) fits a lot better. But the outliers may be present in the middle of the data as well.
A second degree polynomial fits our data good enough, but other curves may be fitted as well. Our goal is to get the y position and slope of the fitted curve at each x.
Excel data available here.