更改密度图图例中的值

Change values in legend of density plot

如何将图例的值从“2”和“3”更改为 "Solid" 和 "Dotted"?

library(ggplot2)

ggplot(mtcars) +
  geom_line(aes(x=mpg,y=cyl,linetype='2')) +
  geom_line(aes(x=mpg,y=disp,linetype='3')) + 
  scale_linetype_discrete(name = "Lines Types  aes") 

ggplot(mtcars) +
  geom_line(aes(x=mpg,y=cyl,linetype='2')) +
  geom_line(aes(x=mpg,y=disp,linetype='3')) + 
  scale_linetype_discrete(name = "Lines Types  aes", labels = c("Solid","Dotted"))