Add a dotted vertical line on certain x-axis values using ggplot

Question

axis values are -6,-4,-2, 0, 2,4, 6 with some y values in a density plot. Is it possible to Add dotted vertical lines on certain x-axis values (Forex: -3 and +3 )using ggplo

Answer 1

Try geom_vline:

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