ggpval

ggpval allows you to perform statistic tests and add the corresponding p-values to ggplots automatically. P-values can be presented numerically or as stars (e.g. *, **). Alternatively, one can also make any text annotation between groups.

Installation

You can install ggpval from github with:

# install.packages("devtools")
devtools::install_github("s6juncheng/ggpval")

Example

Simulate data with groups.

library(ggpval)
library(data.table)
library(ggplot2)
A <- rnorm(200, 0, 3)
B <- rnorm(200, 2, 4)
G <- rep(c("G1", "G2"), each = 100)
dt <- data.table(A, B, G)
dt <- melt(dt, id.vars = "G")

A trivial boxplot example

Give group pairs you want to compare in pairs.

plt <- ggplot(dt, aes(variable, value)) +
  geom_boxplot() +
  geom_jitter()

add_pval(plt, pairs = list(c(1, 2)))

Boxplot with facets

plt <- ggplot(dt, aes(variable, value)) +
  geom_boxplot() +
  geom_jitter() +
  facet_wrap(~G)
add_pval(plt, pairs = list(c(1, 2)))

Bar plot

ggpval try to infer the column which contains the data to do statistical testing. In case this inference was wrong or not possible (for instance the raw data column was not mapped in ggplot object), you can specify the correct column name with response=.

dt[, mu := mean(value),
   by = c("G", "variable")]

dt[, se := sd(value) / .N,
   by = c("G", "variable")]

plt_bar <- ggplot(dt, aes(x=variable, y=mu, fill = variable)) +
  geom_bar(stat = "identity", position = 'dodge') +
  geom_errorbar(aes(ymin=mu-se, ymax=mu+se),
                width = .2) +
  facet_wrap(~G)

add_pval(plt_bar, pairs = list(c(1, 2)), response = 'value')

Additional arguments for statistical function can also be directly supplied.

add_pval(plt_bar, pairs = list(c(1, 2)), 
         test = 't.test',
          alternative = "less",
         response = 'value')

Annotate your plot

add_pval(plt, pairs = list(c(1, 2)), annotation = "Awesome")

In case you want give different annotations to different facets, provide your annotation in a list

add_pval(plt, pairs = list(c(1, 2)), annotation = list("Awesome1", "Awesome2"))

Bugs and issues

Please report bugs and issues on github issue page: https://github.com/s6juncheng/ggpval/issues. Contributions are welcomed.

Acknowledgement

Thanks to Vicente Yépez for testing and helping with improvement of the package.