How To Make Scatterplot with Marginal Histograms in R?

In this article, we will discuss how to make a Scatterplot with Marginal Histograms in the R Language.

To do so we will use the ggExtra package of the R Language. The ggExtra is a collection of functions and layers to enhance ggplot2. The ggMarginal() function can be used to add marginal histograms/boxplots/density plots to ggplot2 scatterplots. 

Installation:

To install the ggExtra package we use:

install.packages("ggExtra")

After installation, we can load the package and use the following function to make a marginal histogram with a scatter plot.

Syntax: ggMarginal( plot, type=”histogram” )

Creating basic scatter plot with marginal histogram:

Here, is a basic scatter plot with marginal histogram using the ggMarginal function of ggExtra package.

R

# load library tidyverse and ggExtra
library(tidyverse)
library(ggExtra)

# set theme
theme_set(theme_bw(12))

# create x and y vector
xAxis <- rnorm(1000)
yAxis <- rnorm(1000) + xAxis + 10

# create sample data frame
sample_data <- data.frame(xAxis, yAxis)

# create scatter plot using ggplot() function
plot <- ggplot(sample_data, aes(x=xAxis, y=yAxis))+
          geom_point()+
        theme(legend.position="none")

# use ggMarginal function to create marginal histogram
ggMarginal(plot, type="histogram")

Output:

Output

Color scatter plot with marginal histogram by group:

To color scatter plot by the group we use the col parameter of ggplot() function. To color the marginal histogram by the group we use groupColour and groupfill as true.

Syntax: ggMarginal( plot, type=”histogram”, groupColour = TRUE, groupFill = TRUE )

Example: Here, we have a scatter plot with marginal histograms both colored by the group. We use boolean values for groupColor and groupFill according to formatting preference.

R

# load library tidyverse and ggExtra
library(tidyverse)
library(ggExtra)

# set theme
theme_set(theme_bw(12))

# create x and y vector
xAxis <- rnorm(1000)
yAxis <- rnorm(1000) + xAxis + 10

# create groups in variable using conditional statements
group <- rep(1, 1000)
group[xAxis > -1.5] <- 2
group[xAxis > -0.5] <- 3
group[xAxis > 0.5] <- 4
group[xAxis > 1.5] <- 5

# create sample data frame
sample_data <- data.frame(xAxis, yAxis, group)

# create scatter plot using ggplot()
# function colored by group
plot <- ggplot(sample_data, aes(x=xAxis, y=yAxis,
                                col = as.factor(group)))+
          geom_point()+
        theme(legend.position="none")

# use ggMarginal function to create marginal histogram
ggMarginal(plot, type="histogram",
           groupColour = TRUE, groupFill = TRUE )

Output:

Output