如何在R语言plotly绘制的箱线图中显示数据点最大最小值的文本标注？

实现思路很简单：先统计每个箱线分组的最大、最小值，再用add_annotations()接口把数值标注到对应位置即可。

完整可运行示例代码（基于你提供的示例改造） #

library(plotly)
# 固定随机种子，结果可复现
set.seed(123)
# 生成和示例对应的两组测试数据
data1 <- rnorm(50)
data2 <- rnorm(50, 1)
# 提前计算每组的极值
min1 <- min(data1)
max1 <- max(data1)
min2 <- min(data2)
max2 <- max(data2)
# 绘图+标注
plot_ly() %>%
  # 绘制两组箱线
  add_trace(x = ~data1, type = "box", name = "组1") %>%
  add_trace(x = ~data2, type = "box", name = "组2") %>%
  # 标注组1最小值
  add_annotations(
    x = min1, y = 0, 
    text = paste0("min: ", round(min1, 2)),
    xanchor = "right",
    showarrow = TRUE,
    arrowhead = 1
  ) %>%
  # 标注组1最大值
  add_annotations(
    x = max1, y = 0,
    text = paste0("max: ", round(max1, 2)),
    xanchor = "left",
    showarrow = TRUE,
    arrowhead = 1
  ) %>%
  # 标注组2最小值
  add_annotations(
    x = min2, y = 1,
    text = paste0("min: ", round(min2, 2)),
    xanchor = "right",
    showarrow = TRUE,
    arrowhead = 1
  ) %>%
  # 标注组2最大值
  add_annotations(
    x = max2, y = 1,
    text = paste0("max: ", round(max2, 2)),
    xanchor = "left",
    showarrow = TRUE,
    arrowhead = 1
  )

参数说明 #

• 水平箱线的分组y坐标默认从0开始按顺序递增，如果你用的是垂直箱线，把坐标逻辑反过来即可：x填分组名，y填极值，用yanchor控制文本位置避免重叠
• round()用来控制显示的小数位数，可按需调整
• 不需要箭头指向极值点的话，把showarrow设为FALSE即可

内容的提问来源于stack exchange，提问作者hk2