使用scale_x_discrete时标签消失问题及ggplot代码求助

Let’s break down why your x-axis labels are vanishing and fix this step by step! I spot a few key issues in your code that are causing the problem:

1. Mismatched Data Type & Scale Type #

If your Times column is numeric (integers 0-23), using scale_x_discrete is incorrect—this scale is designed for categorical variables (like text or factors). Using it on numeric data can cause labels to fail rendering properly.

2. Incomplete Theme Settings #

Your axis.text.x call cuts off with angle = 90, ...—you’re missing critical alignment parameters (vjust and hjust) that ensure rotated labels don’t get clipped outside the plot area.

3. Redundant/Conflicting Scale Parameters #

You defined times = c(0:23) but used it in limits without ensuring your Times data matches that format (e.g., if Times is a factor, numeric limits won’t line up correctly).

Corrected Code (Two Options) #

Pick the one that matches your Times data type:

Option 1: If Times is Numeric (Use Continuous Scale)

This is the better fit for hourly integer values:

times <- 0:23
ggplot(TravelTimes, aes(x = Times)) +
  labs(y = "# Flights", x = "Hour") +
  scale_x_continuous(
    breaks = times,  # Explicitly set all hour ticks
    limits = range(times)  # Ensure full 0-23 range is displayed
  ) +
  geom_point(aes(y = TravelTimes[[2]], colour = "Arrivals", group = 1)) +
  geom_point(aes(y = TravelTimes[[3]], colour = "Departures", group = 1)) +
  geom_line(aes(y = TravelTimes[[2]], colour = "Arrivals", group = 1)) +
  geom_line(aes(y = TravelTimes[[3]], colour = "Departures", group = 1)) +
  theme(
    axis.text.x = element_text(angle = 90, vjust = 0.5, hjust = 1)  # Fix label alignment
  )

Option 2: If You Want Times as a Discrete Factor

First convert Times to a factor to match scale_x_discrete:

# Convert Times to a factor with all 0-23 levels (even if some are missing in data)
TravelTimes$Times <- factor(TravelTimes$Times, levels = 0:23)

ggplot(TravelTimes, aes(x = Times)) +
  labs(y = "# Flights", x = "Hour") +
  scale_x_discrete(
    breaks = 0:23,  # Show all hour labels
    limits = 0:23  # Ensure full range is included
  ) +
  geom_point(aes(y = TravelTimes[[2]], colour = "Arrivals", group = 1)) +
  geom_point(aes(y = TravelTimes[[3]], colour = "Departures", group = 1)) +
  geom_line(aes(y = TravelTimes[[2]], colour = "Arrivals", group = 1)) +
  geom_line(aes(y = TravelTimes[[3]], colour = "Departures", group = 1)) +
  theme(
    axis.text.x = element_text(angle = 90, vjust = 0.5, hjust = 1)  # Fix label clipping
  )

Key Changes Explained: #

• Fixed alignment: Added vjust = 0.5 and hjust = 1 to axis.text.x so rotated labels stay within the plot area.
• Matched scale to data: Used scale_x_continuous for numeric data (more intuitive for hours) or converted Times to a factor for discrete scaling.
• Simplified parameters: Removed redundant name in scale_x since labs(x = "Hour") already sets the axis title.

内容的提问来源于stack exchange，提问作者I.J. Abdul Hakeem