# How To Show Mean Value in Boxplots with ggplot2?

In this article, we will discuss how to show mean value in Boxplot with ggplot2 using R programming language.

Firstly, we will create a basic boxplot using the geom_boxplot() function of the ggplot2 package and then do the needful, so that the difference is apparent.

**Syntax:**

ggplot() + geom_boxplot()

**Example: **Basic boxplot

## R

`# load library tidyverse` `library` `(tidyverse)` `library` `(ggplot2)` ` ` `# basic boxplot` `ggplot` `(diamonds, ` `aes` `(x=cut, y=price)) +` ` ` `# geom_boxplot is used to plot the boxplot` ` ` `geom_boxplot` `()` |

**Output:**

In order to show mean values in boxplot using ggplot2, we use the **stat_summary()** function to compute new summary statistics and add them to the plot. We use stat_summary() function with ggplot() function.

**Syntax:**

stat_summary(mapping = NULL, data = NULL, geom = “pointrange”, position = “identity”, color=”value”, shape=”value”,…)

**Example: **Adding mean value to boxplot

## R

`# load libraries` `library` `(ggplot2)` `library` `(tidyverse)` ` ` `# basic boxplot` `ggplot` `(diamonds, ` `aes` `(x=cut, y=price)) +` ` ` `# geom_boxplot is used to plot the boxplot` ` ` `geom_boxplot` `() +` ` ` `# stat_summary computes the statistics summary` `# fun.y arguments as mean determines that ` `# statistical summary will be mean of y-axis` `stat_summary` `(fun.y=` `"mean"` `)` |

**Output:**

In the output produced above, the point in the center of the boxplot shows the variation of the mean of the y-axis for each category of data on the x-axis.

We can also change the color and shape of the mean mark using the color and shape parameter of the stat_summary() function. This helps us visualize the data better by distinguishing the mark from other symbols.

**Example: **Customizing added mean values

## R

`# load library tidyverse` `library` `(tidyverse)` `library` `(ggplot2)` ` ` `# basic boxplot` `ggplot` `(diamonds, ` `aes` `(x=cut, y=price)) +` ` ` `# geom_boxplot is used to plot the boxplot` ` ` `geom_boxplot` `() +` ` ` `# stat_summary computes the statistics summary` `stat_summary` `(fun.y=` `"mean"` `,color=` `"red"` `, shape=13)` |

**Output:**