Pairwise comparison, TukeyHSD, glht, ANCOVA

Previous Topic Next Topic
 
classic Classic list List threaded Threaded
1 message Options
Reply | Threaded
Open this post in threaded view
|

Pairwise comparison, TukeyHSD, glht, ANCOVA

Wang ChenXi
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




        [[alternative HTML version deleted]]

______________________________________________
[hidden email] 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.