Mancova with R
On Apr 17, 2013, at 16:47 , R?mi Lesmerises wrote:
Dear all, I'm trying to compare two sets of variables, the first set is composed exclusively of numerical variables and the second regroups factors and numerical variables. I can't use a Manova because of this inclusion of numerical variables in the second set. The solution should be to perform a Mancova, but I didn't find any package that allow this type of test. I've already looked in this forum and on the net to find answers, but the only thing I've found is the following: lm(as.matrix(Y) ~ x+z) x and z could be numerical and factors. The problem with that is it actually only perform a succession of lm (or glm), one for each numerical variable contained in the Y matrix. It is not a true MANCOVA that do a significance test (most often a Wald test) for the overall two sets comparison. Such a test is available in SPSS and SAS, but I really want to stay in R! Someone have any idea?
You can fit two models and compare them with (say) fit1 <- lm(as.matrix(Y) ~ x+z) fit2 <- lm(as.matrix(Y) ~ x) anova(fit1, fit2, test="Wilks") or, removing terms sequentially: anova(fit1, test="Wilks")
Thanks in advance for your help! R?mi Lesmerises, biol. M.Sc., Candidat Ph.D. en Biologie Universit? du Qu?bec ? Rimouski remilesmerises at yahoo.ca [[alternative HTML version deleted]]
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