如何在R中实现具有开始日期、结束日期和“中间日期”标记的时间线？

install.packages("ggplot2")

library(ggplot2)

df <- data.frame(start_date = c("2022-01-01", "2022-02-01", "2022-03-01"),
                 end_date = c("2022-01-15", "2022-02-15", "2022-03-15"),
                 middle_date = c("2022-01-08", "2022-02-08", "2022-03-08"))

ggplot() +
  geom_segment(data = df, aes(x = as.Date(start_date), xend = as.Date(end_date),
                              y = 0, yend = 0, color = "Time Line")) +
  geom_point(data = df, aes(x = as.Date(middle_date), y = 0, color = "Middle Date"),
             size = 3) +
  scale_color_manual(values = c("Time Line" = "blue", "Middle Date" = "red"),
                     guide = guide_legend(title = NULL)) +
  labs(x = "Date", y = NULL, title = "Time Line") +
  theme_minimal()