How to draw a line with an arrow below the x-axis?

I’m trying to create a plot in ggplot2 with an arrow line pointing outward, and positioned beneath the x-axis. I used geom_segment function in ggplot2, but its drawing over the plot. I’m want this line with an arrow pointing to the right, positioned below the x-axis, labeled inner left side and outer right side to signify something like an "inner" section.

Here’s the code I have so far:

library(tidyr)
library(ggplot2)
library(grid)  # For arrow customization

# 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
  )

# 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

I tried this also

+ 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

but didnt get arrow line benethe the x axis outside the plot

Kindly correct my code, Thanks in advance

>Solution :

Based on your code a quick option would be to set the limits via coord_cartesian so that the arrow is plotted outside of the panel. Additionally set clip="off" and make some room for the arrow by increasing e.g. the bottom margin of the plot:

library(ggplot2)

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 = -1.5, xend = 10, yend = -1.5), # Line for "inner" section
    arrow = arrow(type = "closed", length = unit(0.2, "inches")),
    color = "blue",
    size = 1.2
  ) +
  annotate("text", x = 3, y = -2, label = "Inner", color = "blue", size = 4) + # Label for inner
  annotate("text", x = 8, y = -2, label = "Outer", color = "red", size = 4) +
  coord_cartesian(clip = "off", ylim = c(0, NA)) +
  theme(plot.margin = margin(5.5, 5.5, 50, 5.5))