To: "Matthew R. Nelson" <mrn@superh.hg.med.umich.edu> Subject: Re: R-beta: Polynomials in lm/glm From: Peter Dalgaard BSA <p.dalgaard@kubism.ku.dk> Date: 15 Aug 1997 15:17:58 +0200 In-Reply-To: "Matthew R. Nelson"'s message of Fri, 15 Aug 1997 07:44:35 -0400 (EDT) "Matthew R. Nelson" <mrn@superh.hg.med.umich.edu> writes: > I was a bit surprised to find that when I attempted to add a polynomial > term to a linear model using either lm or glm as could be done in S > resulted in a fit without that term included and without warning(!!), e.g. > > > lm(response ~ x + x^2, data). > > As far as I can gather, there is no poly() yet in R, and if lm/glm do not > allow functions of variables as their formula arguements, is our only > option to add variables to our dataframe before using lm/glm? I(x^2) should work. We've discussed previously, whether x^2 should do what you expect, and as far as I remember the consensus was positive. In general, one cannot expect to be able to do computations in model formulas (think of autoflu~onset+duration != autoflu~age). -- O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk) FAX: (+45) 35327907 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request@stat.math.ethz.ch =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=