How to plot means inside boxplot using ggplot2 in R?
In this article, we are going to see how to plot means inside boxplot using ggplot in R programming language.
A box plot in base R is used to summarise the distribution of a continuous variable. It can also be used to display the mean of each group. Means or medians can also be computed using a boxplot by labeling points.
Method 1: Using stat_summary method
The ggplot method in R is used to do graph visualizations using the specified data frame. It is used to instantiate a ggplot object. Aesthetic mappings can be created to the plot object to determine the relationship between the x and y-axis respectively. Additional components can be added to the created ggplot object.
Syntax: ggplot(data = NULL, mapping = aes(), fill = )
- data – Default dataset to use for plot.
- mapping – List of aesthetic mappings to use for plot.
Geoms can be added to the plot using various methods. The geom_boxplot() method in R can be used to add box plots in the plots made. It is added as a component to the existing plot. Aesthetic mappings can also contain color attributes which is assigned differently based on different data frames.
geom_boxplot(alpha = )
The method stat_summary() can be used to add mean points to a box plot. It is used to add components to the made plot. This method saves the calculation of mean before plotting the data.
sSyntax: tat_summary(fun=mean, geom=)
- geom – The geometric object to use display the data
- position – The position adjustment to use for overlapping points on this layer
Method 2: Using the aggregate method
Aggregate() method in base R is used to split the data into subsets. It can also be used to compute summary statistics for each of the computed subsets and then return the result in a group by form.
Syntax: aggregate(x, by, FUN)
- x – A list or data frame
- by – The list of the column of the data frame to group by
- FUN – The function to apply to x
The boxplot method in R is used to produce box-and-whisker plot(s) of the specified grouped set of values. The boxplot method in R has the following syntax :
Syntax: boxplot( formula)
- formula – formula, such as y ~ grp, where y is a numeric vector of data values
The boxplot can be customised further to add points and text on the plot.
Syntax: points (x , y , col, pch)
- x ,y – The coordinates of the points to mark
- col – The colour to plot the points with
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