[R] Work around for TukeyHSD names

[Martin Henry H. Stevens]

R Version 2.0.0 Under development (unstable) (2004-05-07)
I have been wanting to use TukeyHSD for two and three way aov's, as 
they are especially simple for students to use correctly. I realize 
model simplification is usually a preferred methodology, but my 
disciplinary enertia and simplicity of TukeyHSD is also compelling.
However, the lack of names on the comparisons for the higher order 
interactions has frustrated us. Here I present a simple, if clumsy 
work-around to provide names for both the tabluar and plot outputs.

ANY FEEDBACK would be appreciated.

My work-around example:

data(warpbreaks)
fm1 <- aov(breaks ~ wool * tension, data = warpbreaks)

a <- TukeyHSD(fm1, "wool:tension") ; a # Gives unlabeled differences

wt <- warpbreaks$tension:warpbreaks$wool # Creates interaction term 
with the correct order of comparisons

b <-TukeyHSD(aov(breaks~wt,warpbreaks))) # Correctly labels differences 
, but provides differences that, I think, are slightly inaccurate.

rowames(a) <- rownames(b) # Provides rownames for the correct 
differences

par(mar=c(5,10,4,2)+0.1)
plot(a, las=1) # Puts correct labels on differences.

Thanks for any comments,
Hank Stevens



Dr. Martin Henry H. Stevens, Assistant Professor
338 Pearson Hall
Botany Department
Miami University
Oxford, OH 45056

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