On Sat, 22 Nov 2003 [EMAIL PROTECTED] wrote: > Hi Folks, > > No doubt a question with a well-known answer, but I'm unfortunately > not managing to find it readily ... ! > > I have a quantitative variable Y and a 4-level ordered factor A > (with very unequal numbers at the different levels, by the way). > > The command > > lm(Y ~ A) > > returns (amongst other stuff) an intercept, and coefficients > A.L, A.Q and A.C for the Linear, Quadratic and Cubic effects. > > I'm trying to verify how R computes A.L, A.Q and A.C (equivalently, > and preferably, what are the definitions of these that correspond > to how R computes them). I haven't touched whatever R's default > settings may be for this operation. > > Can some kind soul enlighten me?
?contr.poly, as the default contrasts set by options("contrasts") specify that for ordered factors. For more details, including how R uses contrasts, see Chapter 6 of MASS (any edition). -- 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