如何使用 ggplot 填充 geom_line() 图下的区域？

Question

I'm trying to fill the area below and above the two lines that are plotted through ggplot. These are the data points that are plotted:

polygon_data <- data.frame(checkpoints=c(650,1625,3250,650,1625,3250), lower=c(-1.17,0.20,1.36,-Inf,-Inf,-Inf), upper=c(2.28,1.75,1.36,Inf,Inf,Inf))
checkpoints_data <- data.frame(checkpoints=c(650,1625,3250),design.lower.bound=c(-1.17,0.20,1.36),design.upper.bound=c(2.28,1.75,1.36))


ggplot()+
  geom_polygon(data=polygon_data,mapping=aes(x=checkpoints, y=lower, fill="red", alpha=0.8))+
  geom_polygon(data=polygon_data,mapping=aes(x=checkpoints, y=upper, fill="green", alpha=0.8))+
  geom_line(checkpoints_data,mapping= aes(x=checkpoints, y=design.upper.bound))+
  geom_line(checkpoints_data,mapping= aes(x=checkpoints, y=design.lower.bound))+
  geom_point(checkpoints_data,mapping= aes(x=checkpoints, y=design.lower.bound))+
  geom_point(checkpoints_data,mapping= aes(x=checkpoints, y=design.upper.bound))

This is what I get instead of having the two areas completely filled. Also colors are not respected by ggplot and I don't understand why:

plot image

Thanks in advance for your help!

Answer 1

I think you have your coordinates incorrect in the polygon_data data frame. c(650, 1625, 3250, 650, 1625, 3250) should be c(650, 1625, 3250, 3250, 1625, 650)

Try this:

polygon_data <- data.frame(checkpoints = c(650, 1625, 3250, 3250, 1625, 650),
                           lower = c(-1.17, 0.20, 1.36, -Inf, -Inf, -Inf),
                           upper = c(2.28, 1.75, 1.36, Inf, Inf, Inf))

Maybe it is also a good idea to put the alpha parameter outside aes() . This avoids getting an extra legend. The legend of fill also looks a bit weird. Maybe it is also a good idea to place fill outside aes() .