Asymmetric expansion of ggplot axis limits

Question

How do you adjust the expansion of limits asymmetrically in ggplot? For example,

library(ggplot2)

ggplot(mtcars) + 
  geom_bar(aes(x = cyl), width = 1)
         


        

Answer 1

ggplot2 v3.0.0 released in July 2018 has expand_scale() option (w/ mult argument) to achieve OP's goal.

Edit: expand_scale() will be deprecated in the future release in favor of expansion(). See News for more information.

library(ggplot2)

### ggplot <= 3.2.1
ggplot(mtcars) + 
  geom_bar(aes(x = cyl, fill = factor(vs)), width = 1) + 
  facet_grid(vs ~ ., scales = "free_y") + 
  scale_y_continuous(expand = expand_scale(mult = c(0, .2))) 

### ggplot >= 3.2.1.9000
ggplot(mtcars) + 
  geom_bar(aes(x = cyl, fill = factor(vs)), width = 1) + 
  facet_grid(vs ~ ., scales = "free_y") + 
  scale_y_continuous(expand = expansion(mult = c(0, .2)))