当不同数量的框时，保留ggplot中框图的宽度

Question

有没有办法在ggplot中保留箱线图的宽度？默认情况下，宽度将根据图中包含的框数而变化。

Answer 1

手动设置x轴怎么样？

# Problem: different widths between these two plots
p1 <- ggplot(mtcars, aes(x=factor(cyl), y=mpg)) + 
  geom_boxplot()

p2 <- ggplot(mtcars[mtcars$cyl<8,], aes(x=factor(cyl), y=mpg)) + 
  geom_boxplot()

# Solution: fix x axis
p3 <- ggplot(mtcars[mtcars$cyl<8,], aes(x=factor(cyl), y=mpg)) + 
  geom_boxplot() + 
  scale_x_discrete(limits=c('4', '6', '8'))

library(gridExtra)
grid.arrange(p1, p2, p1, p3, ncol=2, main='Before', sub='After')