ggsignif

Easily add significance bars to your ggplots

Description

This package provides an easy way to indicate if two groups are significantly different. Commonly this is shown with a by a bar on top connecting the groups of interest which itself is annoted with the level of significance (NS, *, **, ***). The package provides a single layer (geom_signif) that takes the groups for comparison and the test (t.test, wilcox etc.) and adds the annotation to the plot.

Example

Install package

install.packages("ggsignif")

# Or for the latest development version
devtools::install_github("const-ae/ggsignif")

Plot significance

library(ggplot2)
library(ggsignif)
ggplot(mpg, aes(class, hwy)) +
   geom_boxplot() +
   geom_signif(comparisons = list(c("compact", "midsize"), c("minivan", "suv")),
               map_signif_level = TRUE, textsize=5) +
  ylim(NA, 50)

Advanced Example

# Calculate annotation
anno <- t.test(iris[iris$Petal.Width > 1 & iris$Species == "versicolor", "Sepal.Width"], 
               iris[iris$Species == "virginica", "Sepal.Width"])$p.value

# Make plot with custom x and y position of the bracket
ggplot(iris, aes(x=Species, y=Sepal.Width, fill=Petal.Width > 1)) +
  geom_boxplot(position="dodge") +
  geom_signif(annotation=formatC(anno, digits=1),
              y_position=4.05, xmin=2.2, xmax=3, 
              tip_length = c(0.2, 0.04))

For further details go the CRAN page and check the examples in the vignette.