[R] Letters group Games-Howell post hoc in R

David Bars Cortina dbars at tecal.udl.cat
Tue Jan 16 13:50:34 CET 2018

Hello everybody,

I use the sweetpotato database included in R package:

data(sweetpotato) This dataset contains two variables: yield(continous
variable) and virus(factor variable).

Due to Levene test is significant I cannot assume homogeneity of variances
and I apply Welch test in R instead of one-way ANOVA followed by Tukey

Nevertheless, the problems come from when I apply posthoc test. In Tukey
posthoc test I use library(agricolae) and displays me the superscript
letters between virus groups. Therefore there are no problems.

Nevertheless, to perform Games-Howell posthoc, I use
library(userfriendlyscience) and I obtain Games-Howell output but it's
impossible for me to obtain a letter superscript comparison between virus
groups as it is obtained through library(agricolae).

The code used it was the following:



oneway<-oneway(sweetpotato$virus, y=sweetpotato$yield, posthoc =


I try with cld() importing previously library(multcompView) but doesn't work.

Can somebody could helps me?

Thanks in advance,

David Bars.

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