Have you read An Introduction to R or other R tutorial? DO you know about ordered factors and contrasts in linear models?
-- Bert On Wed, Feb 6, 2013 at 5:00 AM, jing tang <gimmyt...@gmail.com> wrote: > Hi, > I am reading the book "Mixed Effects Models in S and S-Plus" and come > across an example with the Rail data. > I tried to use lm(travel~Rail,data=Rail) and got the following result: > > Call: > lm(formula = travel ~ Rail, data = Rail) > > Residuals: > Min 1Q Median 3Q Max > -6.6667 -1.0000 0.1667 1.0000 6.3333 > > Coefficients: > Estimate Std. Error t value Pr(>|t|) > (Intercept) 66.5000 0.9477 70.169 < 2e-16 *** > Rail.L 54.3032 2.3214 23.392 2.22e-11 *** > Rail.Q -4.6917 2.3214 -2.021 0.066161 . > Rail.C -2.6584 2.3214 -1.145 0.274458 > Rail^4 -0.5669 2.3214 -0.244 0.811181 > Rail^5 11.1919 2.3214 4.821 0.000418 *** > --- > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 > > > I wonder how the model is represented. Is it correct to write: Travel = > beta1 + beta2*Rail + error? Beta1 should be Intercept which is clear to me. > But how to link beta2 with the coefficients Rail.L, Rail.Q, Rail.C, Rail^4 > and Rail^5 shown in the result? > > Thanks for your comments, > > Best, > Jing > > [[alternative HTML version deleted]] > > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
