• geom_jitter() 将原始点抖动以避免重叠。
• 叠在 geom_boxplot() 下方。

md_speeding %>% 
  filter(vehicle_color == 'BLUE') %>%
  ggplot(aes(x = gender, y = speed)) +
    # Draw points behind 
    geom_jitter(alpha = 0.3, color = 'steelblue') + 
    # Make transparent
    geom_boxplot(alpha = 0) + 
    labs(title = 'Distribution of speed for blue cars by gender')