使用ggplot在某些x轴值上添加虚线垂直线

Question

轴值为-6,-4,-2,0,2,4,6,密度图中有一些y值.是否可以使用ggplot在某些x轴值(Forex:-3和+3)上添加虚线垂直线？

library(ggplot2)
df <- data.frame(x = rnorm(1000, 0, 1), y = rnorm(1000,
     0, 2), z = rnorm(1000, 2, 1.5))
df.m <- melt(df)
ggplot(df.m) + geom_freqpoly(aes(x = value,
     y = ..density.., colour = variable))

Answer 1

试试geom_vline:

ggplot(df.m) +
  geom_freqpoly(aes(x=value, y=..density.., colour=variable)) +
  geom_vline(xintercept=c(-3,3), linetype="dotted")