指定 alpha 颜色时，地毯图不起作用？

Question

这有效:

plot(1:10, col=rgb(0,0,0,1))
rug(1:10, col=rgb(0,0,0,1))

这不起作用(没有额外绘制地毯):

plot(1:10, col=rgb(0,0,0,0.9))
rug(1:10, col=rgb(0,0,0,0.9))

为什么？我该如何解决这个问题？

我需要这个的原因是因为我想添加 alpha 颜色，以便重叠的“地毯”更暗。无法指定 alpha 颜色，我只能绘制这个:

plot(rep(1:10,100), rep(1:10,100), col=rgb(0,0,0,1))
rug(jitter(rep(1:10,100)), col=rgb(0,0,0,1))

Answer 1

# This is quite easy to do with ggplot2
# data
df = data.frame(x = rep(1:10,100), y = rep(1:10,100))
# code
library(ggplot2)
ggplot(df, aes(x=x, y=y)) + 
  geom_point() + 
  geom_rug(sides="b", position="jitter", alpha=0.2, colour="blue") +
  scale_x_continuous(breaks=seq(0,10,by=2)) +
  scale_y_continuous(breaks=seq(0,10,by=2))