Aesthetics

Aesthetics for bars

geom_bar() and geom_col() can use several aesthetics:

  • alpha
  • color
  • fill
  • linetype
  • size

One of these, color, creates the most surprising results. Predict what the code below will return and then run it.

fill

The color aesthetic controls the outline of each bar in your bar plot, which may not be what you want. To color the interior of each bar, use the fill aesthetic:

Use the code chunk below to experiment with fill, along with other geom_bar() aesthetics, like alpha, linetype, and size.

Width

You can control the width of each bar in your bar chart with the width parameter. In the chunk below, set width = 1, then width = 0.5. Can you spot the difference?

Notice that width is a parameter, not an aesthetic mapping. Hence, you should set width outside of the aes() function.

Exercise 5: Aesthetics

Create a colored bar chart of the class variable from the mpg data set, which comes with ggplot2. Map the interior color of each bar to class.

ggplot(data = mpg) +
  geom_bar(mapping = aes(x = class, fill = class))

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