[R] Dunnett Test in 'multicomp' package

[Richard M. Heiberger]

This example is based on ?glht

> data(warpbreaks)
> glht(amod, linfct = mcp(tension = "Dunnett"))

General Linear Hypotheses

Multiple Comparisons of Means: Dunnett Contrasts


Linear Hypotheses:
           Estimate
M - L == 0    -10.0
H - L == 0    -14.7
> levels(warpbreaks$tension)
[1] "L" "M" "H"
> warpbreaks$tension <- factor(warpbreaks$tension, levels=c("H","M","L"))
>        amod <- aov(breaks ~ tension, data = warpbreaks)
> glht(amod, linfct = mcp(tension = "Dunnett"))

General Linear Hypotheses

Multiple Comparisons of Means: Dunnett Contrasts


Linear Hypotheses:
           Estimate
M - H == 0     4.72
L - H == 0    14.72


Changing the order of the levels is easy.  Rearranging the data itself
is not necessary.

Rich

On Thu, Jun 4, 2015 at 3:42 PM, James F. Henson
<james_henson at suagcenter.com> wrote:
> Greetings
>
> Below is my code.
>
> library("multcomp")
> viaModel1 <- aov(libido ~ dose, data=viagraData)
> dunnettModel <- glht(viaModel1 , linfct = mcp(dose = "Dunnett"), base = "placebo")
>
> The code base="placebo" is ignored.  All treatments are compared to the first treatment in the order, which is "high dose".  It is possible to rearrange the order so that "placebo' is first, but this is inconvenient.
>
> Thanks,
> James F. Henson
>
>         [[alternative HTML version deleted]]
>
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