Thanks for the example. Have you tried fitting a principal curve via either the princurve or pcurve packages? I think this might work for what you want, but no guarantees.
Note that loess, splines, etc. are all fitting y|x, that is, a nonparametric regression of y on x. That is not what you say you want, so these approaches are unlikely to work. -- Bert On Sat, Mar 10, 2012 at 6:20 PM, Emmanuel Levy <emmanuel.l...@gmail.com> wrote: > Hi, > > I'm wondering which function would allow fitting this type of data: > > tmp=rnorm(2000) > X.1 = 5+tmp > Y.1 = 5+ (5*tmp+rnorm(2000)) > tmp=rnorm(100) > X.2 = 9+tmp > Y.2 = 40+ (1.5*tmp+rnorm(100)) > X.3 = 7+ 0.5*runif(500) > Y.3 = 15+20*runif(500) > X = c(X.1,X.2,X.3) > Y = c(Y.1,Y.2,Y.3) > plot(X,Y) > > The problem with loess is that distances for the "goodness of fit" are > calculated on the Y-axis. However, distances would need to be > calculated on the normals of the fitted curve. Is there a function > that provide this option? > > A simple trick in that case consists in swapping X and Y, but I'm > wondering if there is a more general solution? > > Thanks for your input, > > Emmanuel > > ______________________________________________ > 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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.