# Box plot

## Problem

You want to make a box plot.

## Solution

This page shows how to make quick, simple box plots with base graphics. For more sophisticated ones, see Plotting distributions (ggplot2).

### Sample data

The examples here will use the `ToothGrowth`

data set, which has two independent variables, and one dependent variable.

```
head(ToothGrowth)
#> len supp dose
#> 1 4.2 VC 0.5
#> 2 11.5 VC 0.5
#> 3 7.3 VC 0.5
#> 4 5.8 VC 0.5
#> 5 6.4 VC 0.5
#> 6 10.0 VC 0.5
```

Simple box plots of `len`

against `supp`

and `dose`

:

```
boxplot(len ~ supp, data=ToothGrowth)
# Even though `dose` is a numeric variable, `boxplot` will convert it to a factor
boxplot(len ~ dose, data=ToothGrowth)
```

A boxplot of `len`

against `supp`

and `dose`

together.

```
boxplot(len ~ interaction(dose,supp), data=ToothGrowth)
```

Note that `boxplot`

and `plot`

have much the same output, except that `plot`

puts in axis labels, and doesnâ€™t automatically convert numeric variables to factors, as was done with `dose`

above.

```
plot(len ~ interaction(dose,supp), data=ToothGrowth)
```