How to specify aesthetics by group in ggplot

Question

I would like to compare distributions using geom_density, but I want one of the distributions to have no fill. I can describe more easily using the following example:

library(dplyr)
library(ggplot2)
iris %>% ggplot() + 
   geom_density(aes(x = Sepal.Width, color = Species, fill = Species), alpha = 0.5)

How can I make it so that the virginica species is illustrated with a solid black line and no fill?

For example see [this](https://stackoverflow.com/a/65451154/13210554). Using a named vector of colors ensures the right color always goes with the right group. — Dan Adams, Jan 27 '22 at 02:09
How would you specify the empty fill? It appears that NA in scale_color_manual will plug in the default color. — nicholas, Jan 27 '22 at 02:12
Hmm, interesting. Could try `alpha('black', 0)`. Bit of a hack though — Dan Adams, Jan 27 '22 at 02:18
Use "NA" in quotes _e.g._ `+ scale_fill_manual(values = c("red", "green", "NA"))`. — neilfws, Jan 27 '22 at 02:18

score 3 · Accepted Answer · answered Jan 27 '22 at 02:23

iris %>% 
  ggplot(aes(Sepal.Width)) + 
  geom_density(aes(fill = Species), alpha = 0.5) + 
  scale_fill_manual(values = c("setosa" = "red", 
                               "versicolor" = "green", 
                               "virginica" = "NA"))

Result:

How to specify aesthetics by group in ggplot

1 Answers1