2.7 Coordinate Systems

The next term from the Grammar of Graphics that can be specified is the coordinate system. As with scales, coordinate systems are specified with functions that all start with coord_ and are added as a layer. There are a number of different possible coordinate systems to use, including:

• coord_cartesian the default cartesian coordinate system, where you specify x and y values (e.g. allows you to zoom in or out).
• coord_flip a cartesian system with the x and y flipped
• coord_fixed a cartesian system with a “fixed” aspect ratio (e.g., 1.78 for a “widescreen” plot)
• coord_polar a plot using polar coordinates
• coord_quickmap a coordinate system that approximates a good aspect ratio for maps. See documentation for more details.

# zoom in with coord_cartesian
ggplot(mpg, aes(x = displ, y = hwy)) +
  geom_point() +
  coord_cartesian(xlim = c(0, 5))

# flip x and y axis with coord_flip
ggplot(mpg, aes(x = class)) +
  geom_bar() +
  coord_flip()