Summary and Setup

This lesson introduces ggplot2 for learners with basic R experience. It is designed as a short, focused session (approximately 2 hours).

The lesson assumes familiarity with the R language and the RStudio interface. It begins by introducing the grammar of graphics, which underpins how ggplot2 constructs plots. Using the built-in mpg dataset, learners will explore how to create different types of visualisations and how the choice of plot depends on the question being asked.

This lesson focuses on the fundamentals of data visualisation using ggplot2. While examples may reference how plots are used in statistical contexts, it does not cover statistical analysis.

Prerequisite

Participants should have completed an introductory R course (e.g. R for Reproducible Scientific Analysis or have equivalent experience. This includes familiarity with RStudio, running scripts, and working with data frames.

R and RStudio

This lesson assumes you have R and RStudio installed on your computer.

Required R packages

For this lesson we will use the package tidyverse.

The tidyverse is a beginner-friendly collection of R packages designed specifically for data science that share a unified design philosophy, grammar, and data structure. It simplifies data importing, cleaning, and manipulation, making R much more intuitive to learn and read.

R 

install.packages("tidyverse")

ggplot2 is the premier data visualization package within the tidyverse, meaning it automatically loads when you call library(tidyverse) and seamlessly integrates with all other tools in the collection.

Check the package installed correctly by loading the ggplot2 library.

R 

library(ggplot2)

Data

We will use the mpg dataset that is packaged with ggplot.

R 

# View the dataset
head(mpg)

OUTPUT 

# A tibble: 6 × 11
  manufacturer model displ  year   cyl trans      drv     cty   hwy fl    class
  <chr>        <chr> <dbl> <int> <int> <chr>      <chr> <int> <int> <chr> <chr>
1 audi         a4      1.8  1999     4 auto(l5)   f        18    29 p     compact
2 audi         a4      1.8  1999     4 manual(m5) f        21    29 p     compact
3 audi         a4      2    2008     4 manual(m6) f        20    31 p     compact
4 audi         a4      2    2008     4 auto(av)   f        21    30 p     compact
5 audi         a4      2.8  1999     6 auto(l5)   f        16    26 p     compact
6 audi         a4      2.8  1999     6 manual(m5) f        18    26 p     compact