I'm working on a quick tutorial for my students, and was planning on
using Mann-Whitney U as one of the tests.
I have the following (fake) data
grade <- c("MVG", "VG", "VG", "G", "MVG", "G", "VG", "G", "VG")
sex <- c( "male", "male", "female", "male", "female", "male", "female",
"male", "male")
gradesbysex <- data.frame(grade, sex)
The grades is in the Swedish system, where the order is G < VG < MVG
The idea is that they will investigate if they can show a grade
difference by sex (i.e. that the teacher gives better grades to boys or
girls).
Since the wilcox.test needs the order of the grades it wants numeric
vector for the data. Is there a good and simple (i.e. student
compatible) way to handle this? I could tell them to enter data as
numbers instead, but an elegant way to do this inside R would be
preferable.
On the same theme, is there a way to tell barplot that, when making
stacked barplots, to stack the data in a particular order (default
appears to be alphabetical)?
______________________________________________
R-help@r-project.org mailing list
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.
