Grammar of graphics: layers of a plot

• Data

• Geoms

• Aesthetic mappings

• Facets

Data

• The underlying data frame.

• Think rows and columns.

Geoms

• Shapes to represent the data.

• Individual geoms use one shape per row.

• Group geoms use multiple rows to create a shape.

Aesthetic mappings

• Map between the aesthetic properties of a geom and column of the data.

Facets

• Also called small multiples.

• Slice the rows into multiple sub populations.

Identify the components of the grammar of graphics

Identify the components (2)

Scatter plot: Data

• Call the ggplot function and pass in a data frame.

ggplot(df)

Scatter plot: Aesthetic mappings

• Pass the aes function with the mapping as a second argument.

ggplot(df, aes(x=AST, y=TOV))

Scatter plot: Geoms

• Add a layer to use one point to represent one row.

ggplot(df, aes(x=AST, y=TOV)) + geom_point()

More mappings:

• Shape and color

ggplot(df, aes(x=AST, y=TOV, color=Playoff, shape=Playoff)) + 
  geom_point()

Lab 2

• Create a plot to understand the relationship between two pointers made and three pointers made.
• Think about the data and the aesthetic mappings that you want.
• Put it in an Rmarkdown file.