How do I annotate the difference between 2 groups without using the test argument?

[satvirsaggi]

I want to add manual annotations between two groups without performing one of the tests (wilcox, t test, etc.) . However, it seems like I am running into an error.

Warning: Computation failed in stat_signif():
missing value where TRUE/FALSE needed

Is there a way to annotate without having to use one of the tests?

[const-ae]

Hi satvirsaggi,

the error you describe sounds like there are missing values (NA's) in your data.
But anyways, you can add custom annotations to the plot with the annotation parameter for geom_signif():

library(ggplot2)
library(ggsignif)

ggplot(iris, aes(x=Species, y=Sepal.Width)) +
  geom_boxplot() +
  geom_signif(comparisons = list(c("setosa", "versicolor"), c("versicolor", "virginica")),
              annotation = c("Comparison of left and\ncenter boxplot",
                             "Comparison of center and\nright boxplot"),
              step_increase = 0.2) +
  ylim(2, 5.5)

^{Created on 2020-04-16 by the reprex package (v0.3.0)}

I hope this answers your question :)

If not, please provide a short reproducible example with reprex so that I better understand what the problem is.

Best, Constantin