如何在R语言的eCDF图中添加四分位数、均值与中位数

你当前绘制eCDF图的代码如下：

df %>% group_by(group1, group2) %>%   
summarise(n = length(unique(sessionID))) %>%
ggplot(aes(n)) +    
stat_ecdf(geom = "step") +
scale_x_continuous(n.breaks = 30) +   
theme_classic()

要在图中添加四分位数（Q1、Q3）、均值和中位数，可按以下步骤修改代码：

步骤1：提前计算所需统计量 #

先对分组后的数据计算关键统计指标，同时算出这些指标对应的ECDF累积概率（用于确定图上标注的y轴位置）：

# 计算统计量和对应的ECDF值
stats_df <- df %>% 
  group_by(group1, group2) %>%   
  summarise(
    n = length(unique(sessionID)),
    .groups = "drop_last"
  ) %>% 
  mutate(
    ecdf_val = ecdf(n)(n)
  ) %>% 
  group_by(group1, group2) %>% 
  summarise(
    q1 = quantile(n, 0.25),
    q3 = quantile(n, 0.75),
    median = median(n),
    mean = mean(n),
    # 对应统计量的ECDF累积概率值
    q1_ecdf = ecdf(n)(q1),
    q3_ecdf = ecdf(n)(q3),
    median_ecdf = ecdf(n)(median),
    mean_ecdf = ecdf(n)(mean)
  )

步骤2：修改绘图代码，添加统计线和标注 #

在原ggplot代码基础上，用geom_vline添加垂直参考线标记统计量位置，用geom_text添加文本标注：

df %>% 
  group_by(group1, group2) %>%   
  summarise(n = length(unique(sessionID)), .groups = "drop") %>%
  ggplot(aes(n)) +    
  stat_ecdf(geom = "step") +
  # 添加四分位数、中位数、均值的垂直参考线
  geom_vline(data = stats_df, aes(xintercept = q1, color = "Q1"), linetype = "dashed") +
  geom_vline(data = stats_df, aes(xintercept = q3, color = "Q3"), linetype = "dashed") +
  geom_vline(data = stats_df, aes(xintercept = median, color = "中位数"), linetype = "solid") +
  geom_vline(data = stats_df, aes(xintercept = mean, color = "均值"), linetype = "dotdash") +
  # 添加统计量数值标注（可调整hjust/vjust适配你的图）
  geom_text(data = stats_df, aes(x = q1, y = q1_ecdf, label = paste0("Q1: ", round(q1, 1))), 
            hjust = -0.1, vjust = 0.5, size = 3) +
  geom_text(data = stats_df, aes(x = q3, y = q3_ecdf, label = paste0("Q3: ", round(q3, 1))), 
            hjust = -0.1, vjust = 0.5, size = 3) +
  geom_text(data = stats_df, aes(x = median, y = median_ecdf, label = paste0("中位数: ", round(median, 1))), 
            hjust = -0.1, vjust = 0.5, size = 3) +
  geom_text(data = stats_df, aes(x = mean, y = mean_ecdf, label = paste0("均值: ", round(mean, 1))), 
            hjust = -0.1, vjust = 0.5, size = 3) +
  scale_x_continuous(n.breaks = 30) +   
  # 自定义线条颜色
  scale_color_manual(values = c("Q1" = "blue", "Q3" = "blue", "中位数" = "red", "均值" = "green")) +
  labs(color = "统计量") +
  theme_classic() +
  theme(legend.position = "top")

代码说明 #

• stats_df负责计算每个分组的核心统计量，以及这些统计量在ECDF曲线上对应的累积概率，确保标注位置贴合曲线
• 不同统计量用不同颜色、线型的垂直参考线区分，便于识别
• 文本标注的位置可通过hjust（水平对齐）和vjust（垂直对齐）调整，避免遮挡曲线或其他元素
• 通过scale_color_manual自定义颜色，让统计量的视觉区分更清晰

内容的提问来源于stack exchange，提问作者user2845095