Generate expansion vector for scales

This is a convenience function for generating scale expansion vectors for the expand argument of scale_(x|y)_continuous and scale_(x|y)_discrete. The expansion vectors are used to add some space between the data and the axes.

expansion(mult = 0, add = 0)

expand_scale(mult = 0, add = 0)

Arguments

mult	vector of multiplicative range expansion factors. If length 1, both the lower and upper limits of the scale are expanded outwards by mult. If length 2, the lower limit is expanded by mult[1] and the upper limit by mult[2].
add	vector of additive range expansion constants. If length 1, both the lower and upper limits of the scale are expanded outwards by add units. If length 2, the lower limit is expanded by add[1] and the upper limit by add[2].

Examples

# No space below the bars but 10% above them
ggplot(mtcars) +
  geom_bar(aes(x = factor(cyl))) +
  scale_y_continuous(expand = expansion(mult = c(0, .1)))

# Add 2 units of space on the left and right of the data
ggplot(subset(diamonds, carat > 2), aes(cut, clarity)) +
  geom_jitter() +
  scale_x_discrete(expand = expansion(add = 2))

# Reproduce the default range expansion used
# when the 'expand' argument is not specified
ggplot(subset(diamonds, carat > 2), aes(cut, price)) +
  geom_jitter() +
  scale_x_discrete(expand = expansion(add = .6)) +
  scale_y_continuous(expand = expansion(mult = .05))