aes: Define aesthetic mappings.

aes(x = mpg, y = wt) aes(mpg, wt)  # You can also map aesthetics to functions of variables aes(x = mpg ^ 2, y = wt / cyl)  # Aesthetic names are automatically standardised aes(col = x) aes(fg = x) aes(color = x) aes(colour = x)  # aes is almost always used with ggplot() or a layer ggplot(mpg, aes(displ, hwy)) + geom_point() ggplot(mpg) + geom_point(aes(displ, hwy))  # Aesthetics supplied to ggplot() are used as defaults for every layer # you can override them, or supply different aesthetics for each layer