Look at the functions dummy.coef, model.tables, and se.contrasts, they may help with what you want. You can also look at the multcomp package for another approach.
-- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of Christophe Rhodes > Sent: Sunday, September 19, 2010 4:25 AM > To: r-h...@stat.math.ethz.ch > Subject: Re: [R] contr.sum, model summaries and `missing' information > > Christophe Rhodes <cs...@cantab.net> writes: > > > I have a dataset with a response variable and multiple factors with > more > > than two levels, which I have been fitting using lm() or glm(). In > > these fits, I am generally more interested in deviations from the > global > > mean than I am in comparing to a "control" group, so I use > contr.sum() > > as the factor contrasts. I think I'm happy to interpret the > > coefficients in the model summary as the effect of a particular > factor > > level on the deviation from the overall mean; I'm not after a highly > > rigorous treatment of these coefficients and their standard errors, > but > > rather using them as suggestive of further things to investigate. > > > > [...] > > > > As far as I can tell, models m1 and m2 are semantically equivalent. > Is > > there a straightforward way of extracting the standard error and > > t-statistic for the `redundant' comparison directly from m1? I'd > rather > > not have to fit two linear models if I can fit just one. > > Did I post this to the wrong list? I'm still very much interested in > any answer, or a redirection to a more appropriate forum... > > Thanks, > > Christophe > > ______________________________________________ > 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. ______________________________________________ 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.
