koh*_*ske 39
这是通过子集化数据的另一种方法:
ggplot(mtcars, aes(mpg, disp)) + facet_wrap(~cyl) + 
  geom_point(data = subset(mtcars, cyl == 4)) +
  geom_line(data = subset(mtcars, cyl == 6)) +
  geom_text(data = subset(mtcars, cyl == 8), aes(label = gear))
