Dear Iuri, "fake" is not a coefficient in the model:
> linearHypothesis(my_lm, matchCoefs(my_lm, "fake")) Linear hypothesis test Hypothesis: fakeB = 0 Model 1: restricted model Model 2: Infant.Mortality ~ Fertility + fake Res.Df RSS Df Sum of Sq F Pr(>F) 1 45 322.54 2 44 311.97 1 10.567 1.4903 0.2287 Best, John > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > On Behalf Of Iuri Gavronski > Sent: August-15-12 4:47 AM > To: r-help > Subject: [R] car::linearHypothesis fails to constrain factor to zero > > Hi, > > I am trying to test whether a factor (coded as a set of dummy > variables) is equal to zero, using linearHypothesis. I get an error. > See a reproducible example: > > data(swiss) > my_swiss = swiss > my_swiss$fake = factor(sample(c("A","B"),47,rep=T)) > my_lm <- lm(Infant.Mortality ~ Fertility + fake, data=my_swiss) > > > linearHypothesis(my_lm, "fake") > Error in constants(lhs, cnames_symb) : > The hypothesis "fake" is not well formed: contains bad coefficient/variable > names. > In addition: Warning message: > In constants(lhs, cnames_symb) : NAs introduced by coercion > > > > ______________________________________________ > 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.
