In this article, we will discuss how to connect paired points in box plot in ggplot2 in R Programming Language.
Boxplots with data points help us to visualize the summary information between distributions. For example, we may have two quantitative variables corresponding to two different categories and would like to connect those data points by lines. So to do this we have to load the tidyverse library
Syntax:
library(tidyverse)
Example 1: Creating a Boxplot with lines joining paired points
Here is a basic box plot with lines joining paired points.
# load tidyverse library(tidyverse)
# create dataframe sample_data < - data.frame(value=c(1, 2, 3, 4, 4, 5, 6,
7, 9, 11, 1.5, 2.3, 2.5, 3.4,
4.5, 5.5, 6.5, 7.5, 9.5, 12.5),
category=c('A', 'B', 'A', 'B', 'A',
'B', 'A', 'B', 'A', 'B',
'A', 'B', 'A', 'B', 'A',
'B', 'A', 'B', 'A', 'B'),
paired=c(0, 0, 1, 1, 2, 2, 3, 3, 4, 4,
5, 5, 6, 6, 7, 7, 8, 8, 9, 9))
# create plot using ggplot() and geom_boxplot() functions ggplot(sample_data, aes(category, value, fill=category)) +
geom_boxplot()+
# geom_point() is used to make points at data values geom_point()+
# geom_line() joins the paired datapoints geom_line(aes(group=paired))
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Output:
Color Customization:
We can change the color and width of the joining segment by using the color and size property of geom_line().
Syntax:
ggplot(aes( x, y )) + geom_boxplot()+geom_point( aes( fill ), size, shape ) + geom_line( aes( group ), size, color, alpha )
Parameters:
- group: the variable that has pairs to be joined.
- color: the variable that categorizes points
- alpha: determines the transparency
- size: determines the size
- shape: determines the shape
- fill: determines the fill color
Example:
# load tidyverse library(tidyverse)
# create dataframe sample_data <- data.frame( value = c(1,2,3,4,4,5,6,
7,9,11,1.5,2.3,2.5,3.4,
4.5,5.5,6.5,7.5,9.5,12.5),
category = c('A','B','A','B','A',
'B','A','B','A','B',
'A','B','A','B','A',
'B','A','B','A','B'),
paired = c(0,0,1,1,2,2,3,3,4,4,
5,5,6,6,7,7,8,8,9,9))
# create plot using ggplot() and geom_boxplot() functions ggplot(sample_data, aes(category,value, fill=category)) +
geom_boxplot()+
# geom_line() joins the paired datapoints
# color and size parameters are used to customize line
geom_line(aes(group = paired), size=2, color='gray', alpha=0.6)+
# geom_point() is used to make points at data values
# fill and size parameters are used to customize point
geom_point(aes(fill=category,group=paired),size=5,shape=21)
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Output:
Line Customization
We can convert the joining line into ridged line by using linetype property. Every property that works on a line plot also works in this line.
Syntax:
ggplot(aes( x, y )) + geom_boxplot()+geom_point() + geom_line( aes( group ), linetype )
Parameters
- group: the variable that has pairs to be joined.
- linetype: determines the type of line
Example:
# load tidyverse library(tidyverse)
# create dataframe sample_data <- data.frame( value = c(1,2,3,4,4,5,6,
7,9,11,1.5,2.3,2.5,3.4,
4.5,5.5,6.5,7.5,9.5,12.5),
category = c('A','B','A','B','A',
'B','A','B','A','B',
'A','B','A','B','A',
'B','A','B','A','B'),
paired = c(0,0,1,1,2,2,3,3,4,4,
5,5,6,6,7,7,8,8,9,9))
# create plot using ggplot() and geom_boxplot() function ggplot(sample_data, aes(category,value, fill=category)) +
geom_boxplot()+
# linetype parameter is used to customize the joining line geom_line(aes(group = paired), linetype=2, size=1.3)+
# geom_point() is used to plot data points on boxplot geom_point(aes(fill=category,group=paired),size=5,shape=21)
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Output: