Dot Plots in R: Quick Start Guide with Real Life Dataset

To create a dot plot, use the dotchart(data, labels=) function, where data is a “numeric vector”, and “labels” is a vector of labels for each point. It helps compare values of different categories, spot trends, and identify outliers.

The dot plot is a type of data visualization that displays individual data points as dots along an axis. 

It is specifically helpful for small-medium size datasets and can be a good alternative to bar plots and box plots when you want to display all the individual data points.

Example 1: Creating dot plots

Step 1: Install the necessary libraries

Install ggplot2 and tidyverse package for this project. If you have not installed it, then you can install it using this code:

install.packages("ggplot2")

install.packages("tidyverse")

Step 2: Loading the Dataset

For this project, we will use the tcs_stock.csv dataset. You can also find this dataset on Kaggle.

tcs_data <- read.csv("./DataSets/tcs_stock.csv")

head(tcs_data)

Loading the Dataset for dot plots

Step 3: Creating the Dot Chart

Let’s visualize the closing prices over time using a dot chart.

library(ggplot2)

tcs_data <- read.csv("./DataSets/tcs_stock.csv")

# Sorting data by Date to ensure it's plotted chronologically
tcs_data_sorted <- tcs_data[order(as.Date(tcs_data$Date, format="%Y-%m-%d")),]

# Create the dot chart
dotchart(tcs_data_sorted$Close, labels = tcs_data_sorted$Date, 
  main="TCS Stock Closing Prices Over Time", 
  xlab="Closing Price", 
  ylab="Date")

Pictorial representation of the Dot Chart

You can see many dates, so the y-axis labels are crowded.

To make it more appealing, you could consider plotting only a subset of the data, adjusting the plot dimensions, or changing the label display frequency.

Example 2: Changing Point Color

You can change the color of the dots using the col parameter:

dotchart(tcs_data_sorted$Close, labels = tcs_data_sorted$Date, 
  main="TCS Stock Closing Prices Over Time", 
  xlab="Closing Price", 
  ylab="Date",
  col="blue")

Changing Point Color in dot plot

Example 3: Changing Point Character

You can change the plot character of a dot plot using a pch argument.

dotchart(tcs_data_sorted$Close, labels = tcs_data_sorted$Date, 
  main="TCS Stock Closing Prices Over Time", 
  xlab="Closing Price", 
  ylab="Date",
  pch=4) # Using a cross

Changing Point Character in dot plot

Example 4: Changing Label Display Frequency

If there are too many dates and it’s crowded, you can choose to display only every nth label:

library(ggplot2)

tcs_data <- read.csv("./DataSets/tcs_stock.csv")

# Sorting data by Date to ensure it's plotted chronologically
tcs_data_sorted <- tcs_data[order(as.Date(tcs_data$Date, format="%Y-%m-%d")),]

every_nth <- 10 # Display every 10th label
displayed_labels <- c(rep("", every_nth-1), tcs_data_sorted$Date)[1:nrow(tcs_data_sorted)]

dotchart(tcs_data_sorted$Close, labels = displayed_labels, 
  main="TCS Stock Closing Prices Over Time", 
  xlab="Closing Price", 
  ylab="Date")

Changing Label Display Frequency

Example 5: Dot plot by group

In real-life projects, we often plot by group to analyze data thoroughly. 

To demonstrate, I will assume that we want to create a dot plot of the closing prices of TCS stock, grouped by year. This will help us see the distribution of closing prices within each year.

library(ggplot2)

tcs_data <- read.csv("./DataSets/tcs_stock.csv")

# Sorting data by Date to ensure it's plotted chronologically
tcs_data_sorted <- tcs_data[order(as.Date(tcs_data$Date, format="%Y-%m-%d")),]

tcs_data$Year <- format(as.Date(tcs_data$Date, format="%Y-%m-%d"), "%Y")

tcs_data_sorted <- tcs_data[order(tcs_data$Year, as.Date(tcs_data$Date, format="%Y-%m-%d")),]

# Create a color palette
palette <- rainbow(length(unique(tcs_data_sorted$Year)))

dotchart(tcs_data_sorted$Close, labels = tcs_data_sorted$Date, 
  groups = tcs_data_sorted$Year,
  main = "TCS Stock Closing Prices Grouped by Year",
  xlab = "Closing Price",
  ylab = "Date",
  color = palette[tcs_data_sorted$Year])
 legend("topright", legend = unique(tcs_data_sorted$Year), fill = palette, title = "Year")

Dot plot by group in R

Example 6: Dumbbell dot plot

A dumbbell dot plot (or dumbbell chart) is a visualization used to compare two data points for different categories side-by-side.

The two data points are typically represented as dots connected by a line, resembling a dumbbell.

The geom_dumbbell() function comes from the ggalt package. So, you need to install this library.

install.packages("ggalt")

Now, you can create a dumbbell dot plot.

library(ggplot2)
library(ggalt)


tcs_data <- read.csv("./DataSets/tcs_stock.csv")

ggplot(tcs_data, aes(x=Open, xend=Close, y=Date)) +
  geom_dumbbell(size=1.5, color="#555555", 
  point.colour.l = "red", point.colour.r = "blue", 
  point.size.l = 3, point.size.r = 3) +
  labs(title="Comparison of Opening and Closing Prices for TCS Stock", 
  x="Stock Price", 
  y="Date") +
  theme_minimal()

Output

Dumbbell dot plot in R

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