Find inflection points using smooth.spline
T.D.Rudolph <prairie.picker <at> gmail.com> writes:
Is there any way to identify or infer the inflection points in a smooth spline object? I am doing a comparison of various methods of time-series analysis (polynomial regression, spline smoothing, recursive partitioning) and I am specifically interested in obtaining the julian dates associated with the inflection points inferred by the various models. Tyler e.g. http://www.nabble.com/file/p22752459/smooth.spline.pdf smooth.spline.pdf
You can get an analog of first and second derivatives via using first and second differences: ?diff If your spline object is spl, try: diff(diff(spl)) It's possible that you would find lag and rle functions useful as well.
David Winsemius