Hi,
I'm wondering if i can use the function "TukeyHSD" to perform the all pairwise
comparisons of a "aov()" model with one factor (e.g., GROUP) and one continuous
covariate (e.g., AGE). I did for example:
library(multcomp)
data('litter', package = 'multcomp')
litter.aov <- aov(weight ~ gesttime + dose, data = litter)
TukeyHSD(litter.aov, which = 'dose')
and i get a warning message like this:
Warning message:
In replications(paste("~", xx), data = mf): non-factor ignored: gesttime
Is this process above correct? What's the meaning of the warning message? And
does "TukeyHSD" apply to badly unbalanced designs?
In addition, is there any difference between the processes above and below?
litter.mc <- glht(litter.aov, linfct = mcp(dose = 'Tukey'))
summary(litter.mc)
Sincerely,
Sue
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