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 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
