Hello to everyone, after much reading I decided to write because I cannot find a solution to my question.
I already did a priori contrasts before for a continuous variable with normal distribution. Now I have another variable (burrow), which is binomial, and I can do the GLM for it. But when I do the a priori contrasts, it has no result in the cases where all data are 0 (is not that there are no data, they are just all 0 in a category (treat 30-30), and I want to compare this with others that have ones). Data sructure is like this: >head(burrow) date day treat psu sp burrow 1 3 0 30-30 36 B 0 2 3 0 30-30 36 B 0 3 3 0 15-30 36 B 1 4 3 0 15-30 36 B 1 5 3 0 15-30 36 B 1 6 3 0 10-25 36 B 1 My model is this: >model4B2<-glm(burrow~ treat, family=binomial(link="logit"), data=D4B) And I did the contrast like this: >require(multcomp) #Test contrastes 30 vs all (there are 4 categories to compare) k3010R1<-matrix(c(3,-1,-1,-1),1) k3010R1 t3010<-glht(model4B3.2,linfct=k3010R1) summary(t3010) But is not working and I am sure it should work. Could it be because my explanatory variable is cathegorical? Or is just not possible to do contrasts for binomial when you have all 0 in some cathegory? Thank you in advance, -- Rula Domínguez Fernández PhD Student *Departamento de Ecoloxía e Bioloxía Animal* *Faculdade de Ciencias do Mar* *Universidade de Vigo* www.researchgate.net/profile/Rula_Dominguez <https://www.researchgate.net/profile/Rula_Dominguez3> EcoCost <https://ecocost.webs.uvigo.es/index.php?option=com_content&view=article&id=9&Itemid=164&lang=gl> Móvil: +34 646521205 [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org 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.
