Anova posthoc labels on bwplot from lattice in R

Question

I would like to add significance labels following out of post-hoc analysis to box-and-whiskerplots from the function bwplot from the lattice package in R. I have read the ggplot2 -based solution in Posthoc labels on anova boxplot in R however this does not show a solution within the lattice framework. Is there anyone here that has tried this before and could give me some pointers? If there is some way to derive the positions from a bwplot object (as suggested for a regular boxplot object in this article in the R mailing list ) I am guessing I should be looking in that direction? Thanks in advance!

Kind regards,

FM

Answer 1

If you are constructing your plot using interactive commands or a script of several commands, you can always manually add text using grid.text because both lattice and ggplot2 use grid graphics under the hood. So check out this link (because ?grid.text doesn't lead to the page). You'll want to watch your units and you may need to do upViewport(0) to get to the root viewport (depending upon the details of your plotting steps).

Answer 2

I'm not sure where you wanted your labels, but here's an alternative using panel.text .

dd <- data.frame(
  x = runif(120),
  ind = LETTERS[1:6]
)

library(lattice)

bwplot(ind ~ x, data = dd,
       panel = function(x, y, ...) {
         panel.bwplot(x, y, ...)
         panel.text(x = tapply(x, y, median), y, pos = 2, offset = 1, 
                    labels = c("*", "**", "", "", "ns", "***"), ...)
       })