Dear Mario, The interpretation is the same: the average at the reference situation which is the group that has f1 == "f1 level1" and f2 == "f2 level1".
Best regards, ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance Kliniekstraat 25 1070 Anderlecht Belgium To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey 2015-04-26 17:12 GMT+02:00 Mario José Marques-Azevedo <[email protected]> : > Hi all, > > I am doing anova multi factor and I found different Intercept when model > has interaction term. > > I have the follow data: > > set.seed(42) > dt <- data.frame(f1=c(rep("a",5),rep("b",5)), > f2=rep(c("I","II"),5), > y=rnorm(10)) > > When I run > > summary.lm(aov(y ~ f1 * f2, data = dt)) > > The Intercept term is the mean of first level of f1 and f2. I can confirm > that with: > > tapply(dt$y, list(dt$f1, dt$f2), mean) > > I know that others terms are difference of levels with Intercept. > > But I do not know what is Intercept when the model do not have interaction > term: > > summary.lm(aov(y ~f1 + f2, data = dt)) > > I know that I can create a specific contrast table, by I would like > understand the default R output. > > I read contrast sub-chapter on Crawley 2012 (The R book) and in his example > the Intercept is different when model has or not interaction term, but he > explain that Intercept is mean of first level of the factors. > > Best regards, > > Mario > > ............................................................. > Mario José Marques-Azevedo > Ph.D. Candidate in Ecology > Dept. Plant Biology, Institute of Biology > University of Campinas - UNICAMP > Campinas, São Paulo, Brazil > > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] mailing list -- To UNSUBSCRIBE and more, see > 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. [[alternative HTML version deleted]] ______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see 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.
