I appreciate your quick reply. I am using the model of the following structure :
fit <- gam(y~x1+s(x2)) ,where y, x1, and x2 are quantitative variables. So the response distribution is assumed to be gaussian(default). Now I understand that the data size was too small. Thank you. Best Wishes, Ariyo 2007/10/3, Simon Wood <[EMAIL PROTECTED]>: > What sort of model structure are you using? In particular what is the response > distribution? For poisson and binomial then overfitting can be a sign of > overdispersion and quasipoisson or quasibinomial may be better. Also I would > not expect to get useful smoothing parameter estimates from 10 data! > > best, > Simon > > On Wednesday 03 October 2007 06:55, 神野有生 wrote: > > Dear listers, > > > > I'm using gam(from mgcv) for semi-parametric regression on small and > > noisy datasets(10 to 200 > > observations), and facing a problem of overfitting. > > > > According to the book(Simon N. Wood / Generalized Additive Models: An > > Introduction with R), it is > > suggested to avoid overfitting by inflating the effective degrees of > > freedom in GCV evaluation with > > increased "gamma" value(e.g. 1.4). But in my case, it didn't make a > > significant change in the > > results. > > > > The only way I've found to suppress overfitting is to set the basis > > dimension "k" at very low values > > (3 to 5). However, I don't think this is reasonable because knots > > selection will then be an > > important issue. > > > > Is there any other means to avoid overfitting when alalyzing small > > datasets? > > > > Thank you for your help in advance, > > Ariyo Kanno > > > > -- > > Ariyo Kanno > > 1st-year doctor's degree student at > > Institute of Environmental Studies, > > The University of Tokyo > > > > ______________________________________________ > > 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. > > -- > > Simon Wood, Mathematical Sciences, University of Bath, Bath, BA2 7AY UK > > +44 1225 386603 www.maths.bath.ac.uk/~sw283 > > ______________________________________________ > 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.
