making line legends for geom_density in ggplot2 in R

Question

with ggplot2, I make the following density plot:

ggplot(iris) + geom_density(aes(x=Sepal.Width, colour=Species))

The colour legend (for each Species value) appears as a box with a line through it, but the density plotted is a line. Is there a way to make the legend appear as just a colored line for each entry of Species, rather than a box with a line through it?

Answer 1

One possibility is to use stat_density() with geom="line". Only in this case there will be only upper lines.

  ggplot(iris)+
    stat_density(aes(x=Sepal.Width, colour=Species),
                     geom="line",position="identity")

If you need also the whole area (all lines) then you can combine geom_density() with show_guide=FALSE (to remove legend) and stat_density() than will add legend just with horizontal lines.

ggplot(iris) + 
  geom_density(aes(x=Sepal.Width, colour=Species),show_guide=FALSE)+
  stat_density(aes(x=Sepal.Width, colour=Species),
                  geom="line",position="identity")