r - R中带有水平标记和星号的条形图（ggplot等）

Question

使用 R 的标准情节或更好的 GGPLOT，有没有办法创建这样的情节？请特别注意选定条上带有星号的水平线。

Answer 1

I don't know of an easy way to annotate graphs like this in ggplot2. Here's a relatively generic approach to make the data you'd need to plot. You can use a similar approach to annotate the relationships as necessary. I'll use the iris dataset as an example:

library(ggplot2)
library(plyr) #for summarizing data

#summarize average sepal length by species
dat <- ddply(iris, "Species", summarize, length = mean(Sepal.Length))

#Create the data you'll need to plot for the horizontal lines
horzlines <- data.frame(x    = 1, 
                        xend = seq_along(dat$Species)[-1],
                        y    = seq(from = max(dat$length), by = 0.5, length.out = length(unique(dat$Species))-1),
                        yend = seq(from = max(dat$length), by = 0.5, length.out = length(unique(dat$Species))-1),
                        label = c("foo", "bar")
)

ggplot() + 
  geom_histogram(data = dat, aes(Species, length), stat = "identity") +
  geom_segment(data = horzlines, aes(x = x, xend = xend, y = y, yend = yend)) +
  geom_text(data = horzlines, aes(x = (x + xend)/2, y = y + .25, label = label))

Giving you something like this: