ggplot2 layers

Introduction to Data Visualization with ggplot2

Rick Scavetta

Founder, Scavetta Academy

ggplot2 package

  • The grammar of graphics implemented in R
  • Two key concepts:
    1. Layer grammatical elements
    2. Aesthetic mappings
Introduction to Data Visualization with ggplot2

Data

Introduction to Data Visualization with ggplot2

Iris dataset

1 Fisher, R. A. (1936) The use of multiple measurements in taxonomic problems. Annals of Eugenics, 7, Part II, 179–188. 2 Anderson, Edgar (1935). The irises of the Gaspe Peninsula, Bulletin of the American Iris Society, 59, 2–5.
Introduction to Data Visualization with ggplot2

Iris dataset

iris
    Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
1            5.1         3.5          1.4         0.2     setosa
2            4.9         3.0          1.4         0.2     setosa
3            4.7         3.2          1.3         0.2     setosa
...
50           5.0         3.3          1.4         0.2     setosa
51           7.0         3.2          4.7         1.4 versicolor
52           6.4         3.2          4.5         1.5 versicolor
53           6.9         3.1          4.9         1.5 versicolor
...
100          5.7         2.8          4.1         1.3 versicolor
101          6.3         3.3          6.0         2.5  virginica
102          5.8         2.7          5.1         1.9  virginica
103          7.1         3.0          5.9         2.1  virginica
...
150          5.9         3.0          5.1         1.8  virginica
Introduction to Data Visualization with ggplot2

Aesthetics

Introduction to Data Visualization with ggplot2

Iris aesthetics

Introduction to Data Visualization with ggplot2

Geometries

Introduction to Data Visualization with ggplot2

Iris geometries

g <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width)) +
  geom_jitter()
g

Introduction to Data Visualization with ggplot2

Themes

Introduction to Data Visualization with ggplot2

Iris themes

g <- g +
  labs(x = "Sepal Length (cm)", y = "Sepal Width (cm)") +
  theme_classic()
g

Introduction to Data Visualization with ggplot2

Let's practice!

Introduction to Data Visualization with ggplot2

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