On Fri, 9 Apr 2004, Rafael A. Irizarry wrote: > hi! > > i want to change the "robustness weights" used by loess. these > are described on page 316 of chambers and hastie's "statistical models in S" > book as > > r_i = B(e_i,6m) > > where B is tukey's biweight function, e_i are the residulas, and m is the > median average distance from 0 of the residuals. i want to > change 6m to, say, 3m. > > is there a way to do this? i cant figure it out from the help files.
Well, they say loess in R is an interface to C/Fortran code, and not the same code as the S code described in Chambers & Hastie. I translated the C driver routines to R for some added flexibility. At a quick look, in function simpleLoess() you will find the weights in object `robust', calculated by Fortran function lowesw. You could replace that by a call to an R-level alternative, or play with the Fortran source code. You'll have to do what I did way back, and read the source code to see how it works in detail. -- 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
