R 如何在x轴下方画一条带有箭头的线

我试图创建一个以{ggplot2}为单位的图，其中箭头线向外指向，并位于x轴下方.我在{ggplot2}中使用了geom_segment函数，但它已经绘制了情节.我希望这条线有一个指向右侧的箭头，位于x轴下方，标记为内左侧和外右侧，以表示类似于"内"部分的东西.

Data

library(tidyr)
# Define the vectors
st <- c("a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10")
y1 <- c(5, 1, 4, 6, 2, 3, 7, 8, 2, 8)                   # Create more example data
y2 <- c(3, 3, 3, 3, 4, 4, 5, 5, 7, 7)
# Create a data frame
df <- data.frame(st = st, y1 = y1, y2 = y2)

# Pivot from wide to long
df_long <- df %>%
  pivot_longer(
    cols = c("y1", "y2"),  # Columns to pivot
    names_to = "variable",       # Column name for variable names
    values_to = "value"          # Column name for values
  )

Code

library(ggplot2)
library(grid)  # For arrow customization
# Create the plot
ggplot(data = df_long, aes(x = st, y = value, color = variable, group = variable)) +
  geom_line(size = 1.2) +  # Adjust line thickness
  labs(
    title = "Line Plot with Arrow Beneath X-Axis",
    x = "Identifier",
    y = "Value",
    color = "Variable"
  ) +
  theme_minimal() +  # Use a clean theme for better visualization
  geom_segment(
    aes(x = 1, y = -1, xend = 10, yend = -1),  # Line for "inner" section
    arrow = arrow(type = "closed", length = unit(0.2, "inches")),
    color = "blue",
    size = 1.2
  )  +
  annotate("text", x = 3, y = -1.5, label = "Inner", color = "blue", size = 4) +  # Label for inner
  annotate("text", x = 8, y = -1.5, label = "Outer", color = "red", size = 4)  # Label for outer

我也try 过这个，

+ geom_line(size = 1.2) +  # Adjust line thickness
  geom_hline(yintercept = 0, linetype = "dashed") +  # Add horizontal line at y = 0
  geom_vline(xintercept = -1, linetype = "dashed") +  # Add vertical line at x = 0

但在图外的x轴下方没有箭头线.