search for: plr1

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2008 Sep 30
2
weird behavior of drop1() for polr models (MASS)
...expected for regular main effects models, however when the model includes an interaction effect it seems to have problems with matching the parameters to the predictor terms. An example: library("MASS"); options(contrasts = c("contr.treatment", "contr.poly")); house.plr1 <- polr(Sat ~ Infl + Type + Cont, weights = Freq, data = housing); drop1(house.plr1,attributes(house.plr1$terms)$term.labels,test="Chisq"); house.plr2 <- polr(Sat ~ Infl * Type + Cont, weights = Freq, data = housing); drop1(house.plr2,attributes(house.plr2$terms)$term.labels,test=...