Dear Prof Ripley, > > Hello, > > > > I am interested in performing a 2D loess smooth on microarray data, i.e. > > log2 ratios on a 2D grid, using different spans in the horizontal and > > vertical directions (the immediate reason being that replicate spots are > > laid out in the horizontal direction). Is it possible to do this in R? > > Functions like loess(stats) seem to apply the same span for all > > predictors, which carries over to functions like ma2D(marray). > > See the next comment. 'span' applies to 2D distances, and I think you > need to rescale your inputs so Euclidean distance is appropriate.
That's a great idea. > > > As an elementary second question, are there circumstances where one > > expects to see a substantial difference in the fits between say loess(y > > ~ x1 + x2) and loess(y ~ x1 * x2) with an interaction term (and if so, > > what are they)? > > From the help page: > > formula: a formula specifying the numeric response and one to four > numeric predictors (best specified via an interaction, but > can also be specified additively). Will be coerced to a > formula if necessary. > > So the two versions both specify smoothing in 2D. > > You can use things like lo(x1) + lo(x2) in some gam fits. Hadn't thought of that, I will explore this. > > It often helps to read the primary sources, in this case chapters in the > White Book (Chambers & Hastie, nominally 1992, actually published in > 1991). > > -- > Brian D. Ripley, [EMAIL PROTECTED] > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > Thanks very much for the help. Nice photos on the Web, by the way. Regards, _Taku Taku A. Tokuyasu, PhD UCSF Helen Diller Family Comprehensive Cancer Center San Francisco, CA 94143-0808 ______________________________________________ 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.
