How to generate a compact letter display for pairwise TukeyHSD

问题

I'm having trouble generating a compact letter display for my results. I've run an ANOVA followed by Tukey's HSD to generate the p values for each pair, but I do not know how (or if it is possible?) to assign letters to these p values to show which pairs are significant from each other.

csa.anova<-aov(rate~temp*light,data=csa.per.chl) summary(csa.anova) TukeyHSD(csa.anova)

This runs the tests I need, but I don't know how to assign letters to each p value to show which pairs are significant.

回答1:

You need to install the multcomp package first. It can compute the Tukey HSD Test and returns an object that has summary and plot methods. The package also has a function (cld) to print the "compact letter display." As an example we can use the iris data set that comes with R:

library(multcomp)
data(iris)
iris.aov <- aov(Petal.Length~Species, iris)
iris.tukey <- glht(iris.aov, linfct=mcp(Species="Tukey"))
cld(iris.tukey)
#     setosa versicolor  virginica 
#        "a"        "b"        "c" 

回答2:

I cannot make this code work:

data("iris")
iris.aov<-aov(Petal.Length~Species,iris)
iris.tukey<-glht(iris.aov,linfct=mcp(Species="Tukey"))

Here is the error triggered:

Error in glht(iris.aov, linfct = mcp(Species = "Tukey")) : could not find function "glht"

来源：https://stackoverflow.com/questions/57737598/how-to-generate-a-compact-letter-display-for-pairwise-tukeyhsd