ggplot2中geom_errorbar多变量按upper值降序排序问题

原始代码与需求 #

以下是生成初始可视化的代码：

library(ggplot2)
mydat <- data.frame(mean = c(23, 24, 15, 27, 18, 19, 23, 20, 32),
           lower = c(20, 19, 13, 15, 14, 18, 20, 17, 20),
           upper = c(25, 29, 17, 39, 22, 20, 26, 23, 40),
           class = c("A", "B", "C", "A", "B", "C", "A", "B", "C"),
           domain = c("North", "North", "North", "West", "West", "West", "South", "South", "South"))
mydat$class <- as.factor(mydat$class)
mydat$domain <- as.factor(mydat$domain)

mydat %>% ggplot(aes(x = mean, y = class, color = domain, Group = domain, xmin = lower, xmax = upper)) +
  geom_errorbar(width = 0.1, position = position_dodge(width = 0.5)) + theme_light() + geom_point(position = position_dodge(width = 0.5)) + xlab("Counts")

当前生成的可视化效果如图所示，需求为：让geom_errorbar同时在每个class分组内以及跨domain维度，按照errorbar的upper边界值降序排列，目标效果如图所示。

尝试过的无效代码 #

曾使用forcats包调整因子顺序，但未达到预期：

library(forcats)
mydat %>% ggplot(aes(x = mean, y = class, color = fct_infreq(domain), Group = fct_infreq(domain), xmin = lower, xmax = upper)) +
  geom_errorbar(width = 0.1, position = position_dodge(width = 0.5)) + theme_light() + geom_point(position = position_dodge(width = 0.5)) + xlab("Counts")

正确实现方法 #

要实现需求，需同时调整class在y轴的排序（跨维度按upper降序），以及每个class内domain的 dodge 顺序（分组内按upper降序），完整代码如下：

library(ggplot2)
library(dplyr)
library(forcats)

mydat <- data.frame(mean = c(23, 24, 15, 27, 18, 19, 23, 20, 32),
           lower = c(20, 19, 13, 15, 14, 18, 20, 17, 20),
           upper = c(25, 29, 17, 39, 22, 20, 26, 23, 40),
           class = c("A", "B", "C", "A", "B", "C", "A", "B", "C"),
           domain = c("North", "North", "North", "West", "West", "West", "South", "South", "South")) %>%
  mutate(class = as.factor(class),
         domain = as.factor(domain)) %>%
  # 1. 按class分组计算组内最大upper值，以此对class因子降序重排
  group_by(class) %>%
  mutate(class_max_upper = max(upper)) %>%
  ungroup() %>%
  mutate(class = fct_reorder(class, -class_max_upper)) %>%
  # 2. 按class分组，对domain按自身upper值降序重排，生成控制dodge顺序的新因子
  group_by(class) %>%
  mutate(domain_ordered = fct_reorder(domain, -upper)) %>%
  ungroup()

# 绘制图形
mydat %>%
  ggplot(aes(x = mean, y = class, color = domain, 
             group = domain_ordered, # 用排序后的因子控制分组内的dodge顺序
             xmin = lower, xmax = upper)) +
  geom_errorbar(width = 0.1, position = position_dodge(width = 0.5)) +
  geom_point(position = position_dodge(width = 0.5)) +
  theme_light() +
  xlab("Counts")

代码说明 #

• fct_reorder(class, -class_max_upper)：将y轴的class因子按每个组的最大upper值降序排列，实现跨维度的整体排序；
• fct_reorder(domain, -upper)：在每个class分组内，将domain按自身的upper值降序排列，生成的domain_ordered作为group参数的依据，控制误差棒在分组内的显示顺序；
• position_dodge(width = 0.5)：确保重新排序后的分组能正确错开，避免重叠。

内容的提问来源于stack exchange，提问作者Adrian