You are wrong about S-PLUS! contr.poly only takes as argument the number of levels required (and uses pre-computed sets for up to 12 levels). You get orthogonal polynomials for equally-space values from contr.poly in both systems, as documented.
I don't think you are describing contrasts for an ordered factor, but orthogonal polynomials in a numeric variable. The latter are computed by the function poly() in both R and S-PLUS. You could set them up to give a contrasts matrix if you want, but not a contrasts function (as that is only passed the number of levels, AFAIR). On Thu, 16 Jan 2003, George W. Gilchrist wrote: > In S-Plus, I can obtain polynomial contrasts for an ordered factor with > contr.poly(). The function also exists in R, however is limited to factors > where the levels are equally spaced. In S-Plus, one can obtain the contrasts > for a set of numeric values representing unequally spaced ordered factors. > Has anyone implemented this in R? I see that the S-Plus function calls > another function (poly.raw()) that calls a Fortran routine. Thanks for your > assistance. -- 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 http://www.stat.math.ethz.ch/mailman/listinfo/r-help
