Hello Bert, Thanks so much for these suggestions. They led me to the package "LPCM", which I found worked best with minimum tuning.
lpc1 = lpc(cbind(X,Y), scaled=TRUE, h=c(0.05,0.05)) plot(lpc1) ... et voila! All the best, Emmanuel On 11 March 2012 00:37, Bert Gunter <gunter.ber...@gene.com> wrote: > 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.
