I am pretty pleased with baselines I fit to chromatograms using the
runquantile() function in caTools(v1.6) when its probs parameter is
set to 0.2 and its k parameter to ~1/20th of n (e.g., k ~ 225 for n ~
4500, where n is time series length). This ignores occasional low-
side outliers, and,
I am not surprised at slowness of runquantile, since it is trying to
perform n=4500 partial sorts of k=225 elements. Here are some thoughts
at speeding it up:
1) playing with different endrule settings can save some time, but
usually results with undesirable effects at first and last 112 values.