Add an extra legend to facet in ggplot

I want to add few individual data points to selected facet and have a legend for them.

library(ggplot2)

ggplot(data=mpg, aes(displ, hwy)) +
  geom_bin2d()+
  facet_wrap(~class) + 
  geom_point(data = data.frame(displ = c(5,3,6,4), hwy = c(25,30,35,27), type="XX", class = "pickup"), colour="blue")

With this I get the legend for counts but how can I add a custom legend for the added points with XX as legend?

>Solution :

If you want to have a legend you have to map on aesthetics, i.e. move color= inside aes() and set your desired color via scale_color_manual:

library(ggplot2)

ggplot(data = mpg, aes(displ, hwy)) +
  geom_bin2d() +
  facet_wrap(~class) +
  geom_point(data = data.frame(
    displ = c(5, 3, 6, 4), 
    hwy = c(25, 30, 35, 27), 
    type = "XX", class = "pickup"), 
    aes(colour = type)) +
  scale_color_manual(values = "blue")