The ggplot2 library allows to make a boxplot using geom_boxplot(). You have to specify a quantitative variable for the Y axis, and a qualitative variable for the X axis ( a group).
# Load ggplot2
library(ggplot2)
# The mtcars dataset is natively available
# head(mtcars)
# A really basic boxplot.
ggplot(mtcars, aes(x=as.factor(cyl), y=mpg)) +
geom_boxplot(fill="slateblue", alpha=0.2) +
xlab("cyl")
