How do I create a box plot in R with ggplot2?

Use geom_boxplot() from the ggplot2 package. Variables needed: 1 numerical + 0-1 categorical.

What data types work with a box plot?

A box plot works best with categorical, numerical data. It requires 1 numerical + 0-1 categorical.

DistributionComparison CategoricalNumerical

Box Plot

ggplot2: geom_boxplot() · Package: ggplot2 · Variables: 1 numerical + 0-1 categorical

WHAT IS A BOX PLOT?

A box plot (also called a box-and-whisker plot) provides a compact five-number summary: minimum, first quartile (Q1), median, third quartile (Q3), and maximum — with outliers shown as individual points. It is the most space-efficient way to compare distributions across multiple groups. Box plots answer "how does the spread and center of group A compare to group B?" They work well with 3-20 groups and are standard in scientific and statistical reporting. Note that box plots hide distribution shape (bimodality) — consider violin plots if shape matters. In ggplot2, use geom_boxplot().

BEST FOR

· Comparing distributions across groups
· Identifying outliers
· Compact summary
· 3-20 groups

AVOID WHEN

· Non-technical audience
· When distribution shape matters (bimodality hidden)
· Very small samples

R + GGPLOT2 CODE EXAMPLE

ggplot2

ggplot(mtcars, aes(x = factor(cyl), y = mpg)) +
  geom_boxplot(fill = "#ff6a00", alpha = 0.7) +
  labs(title = "MPG by Cylinder Count", x = "Cylinders", y = "MPG")