# How to Draw Boxplots with Mean Values in R (With Examples)

You can use the following methods to draw a boxplot with a mean value in R:

Method 1: Use Base R

```#create boxplots
boxplot(df\$values~df\$group)

#calculate mean value by group
means <- tapply(df\$values, df\$group, mean)

#add means as circles to each boxplot
points(means, pch=20) ```

Method 2: Use ggplot2

```library(ggplot2)

#create boxplots with mean values shown as circles
ggplot(df, aes(x=group, y=values, fill=group)) +
geom_boxplot() +
stat_summary(fun=mean, geom='point', shape=20)
```

The following examples show how to use each method in practice with the following data frame in R:

```#create data frame
df <- data.frame(team=rep(c('A', 'B', 'C'), each=5),
points=c(4, 4, 5, 6, 8, 7, 6, 8, 9, 12,
11, 12, 13, 16, 18))

#view first six rows of data frame

team points
1    A      4
2    A      4
3    A      5
4    A      6
5    A      8
6    B      7
```

### Example 1: Create Boxplots with Mean Values in Base R

The following code shows how to create boxplots with mean values in base R:

```#create boxplots
boxplot(df\$points~df\$team)

#calculate mean value by group
means <- tapply(df\$points, df\$team, mean)

#add means as circles to each boxplot
points(means, pch=20, cex=1.5)``` The black lines inside each boxplot represent the median value and the black circles inside each boxplot represent the mean value.

Note: Change the value for the cex argument to change the circle size.

### Example 2: Create Boxplots with Mean Values in ggplot2

The following code shows how to create boxplots with mean values in ggplot2:

```library(ggplot2)

#create boxplots with mean values
ggplot(df, aes(x=team, y=points, fill=team)) +
geom_boxplot() +
stat_summary(fun=mean, geom='point', shape=20, size=8) +
theme(legend.position='none')``` The black lines inside each boxplot represent the median value and the black circles inside each boxplot represent the mean value.

Note: Change the value for the size argument within the stat_summary() function to change the circle size.