I don't see why one would want to pretend that the function is continuous. It isn't. The x variable devices is discrete. Moreover, the whole solution space is small: the possible solutions are integers in the range of maybe 20-30.
Bill On Fri, Jun 18, 2010 at 9:00 AM, José E. Lozano <lozal...@jcyl.es> wrote: > >>> How about smoothing the percentages, and then take the second >>> derrivative to find the inflection point? >>> >>> which.max(diff(diff((lowess(percentages)$y)))) >> >> This solution is what I've been using so far. The only difference is that > I am smoothing the 1st derivative, since its >> the one I want to be smooth, smoothing the percentages curve does not > produce good results. > > I've noticed something: > > What I am using is something like: > > which.max(abs(diff(sign(diff(diff(lowess(percentages)$y)))))) > > "The fist value where the 2nd derivative changes its sign" To find the > f''(x)=0 > > But you have suggested the max value of the 2nd derivative. > > Regards, > Jose Lozano > > ______________________________________________ > 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. > ______________________________________________ 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.
