5.3 Aesthetic Mapings

# using color
ggplot(data = mpg) + geom_point(mapping = aes(x = displ, y = hwy, color = class))

# using size
ggplot(data = mpg) + geom_point(mapping = aes(x = displ, y = hwy, size = class))
## Warning: Using size for a discrete variable is not advised.

# using alpha
ggplot(data = mpg) + geom_point(mapping = aes(x = displ, y = hwy, alpha = class))

# using shape
ggplot(data = mpg) + geom_point(mapping = aes(x = displ, y = hwy, shape = class))
## Warning: The shape palette can deal with a maximum of 6 discrete values
## because more than 6 becomes difficult to discriminate; you have 7.
## Consider specifying shapes manually if you must have them.
## Warning: Removed 62 rows containing missing values (geom_point).

# manual set property
# note color is not in the aes
ggplot(data = mpg) + geom_point(mapping = aes(x = displ, y = hwy), color = "blue")

# if you put a variable outside you will get an error
ggplot(data = mpg) + geom_point(mapping = aes(x = displ, y = hwy), color = class)