roger koenker wrote: > you can do: > > X <- model.matrix(formula, data = your.data) > > > url: www.econ.uiuc.edu/~roger Roger Koenker
Or use a simpler basis such as the truncated power basis, and rely on accuracy of modern matrix algebra routines to handle the non-orthogonality: library(Design) f <- fittingfunction(y ~ rcs(age,5)+sex) Function(f) # see algebraic form latex(f) # see nicely typeset algebraic form publish2Web(f) # Planned future function for evaluating models on the web using R's predict( ) function Frank Harrell > email [EMAIL PROTECTED] Department of Economics > vox: 217-333-4558 University of Illinois > fax: 217-244-6678 Champaign, IL 61820 > > > On Dec 5, 2005, at 7:36 AM, Stephen A Roberts wrote: > > >>Greetings, >> >>I have a model fitted using bs() and need to be able to write down >>a closed form for the spline function to enable the use of the >>fitted model outside R. Does anyone know a simple way of extracting >>the piecewise cubics from the coefficients and knots? As far as I >>know they are defined by recurrence relationships, but the R >>implementation is buried in C code, and I guess in non-trivial to >>invert. I know about predict.bs() within R, but I want the full >>piecewise cubic. >> >>Steve. >> >> Dr Steve Roberts >> [EMAIL PROTECTED] >> >>Senior Lecturer in Medical Statistics, >>Biostatistics Group, >>University of Manchester, >> >>______________________________________________ >>R-help@stat.math.ethz.ch mailing list >>https://stat.ethz.ch/mailman/listinfo/r-help >>PLEASE do read the posting guide! http://www.R-project.org/posting- >>guide.html > > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > -- Frank E Harrell Jr Professor and Chair School of Medicine Department of Biostatistics Vanderbilt University ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html