如何使用geom_bar在x轴展示两个分类变量并添加区域分隔线

实现方案 #

你可以通过geom_vline()添加垂直分隔线，搭配annotate()添加分组标签即可实现需求，修改后的完整可运行代码如下：

library(dplyr)
library(ggplot2)
data <- tibble::tribble(
  ~code,    ~term,          ~estimate,           ~std.error,       ~statistic,             ~p.value,      ~region,
  "ANTA", "t_chla", 0.0577051712200805, 0.000720537559840254, 80.0862778518777, 1.51491004165028e-36,      "Polar",
  "ARCH", "t_chla", 0.0528096415790542,  0.00237431411186973, 22.2420619559337, 9.38778083531695e-08, "Equatorial",
  "ARCT", "t_chla", 0.0381489725623347, 0.000549351930679462, 69.4435942277484,  7.1661522966813e-84,      "Polar",
  "BPLR", "t_chla", 0.0334314725309052, 0.000908084662707285, 36.8153696498248,   6.728272457306e-26,      "Polar",
  "EMED", "t_chla",  0.048713647973686,  0.00179735526256328, 27.1029601038437, 1.37127584382531e-20,  "Temperate",
  "SANT", "t_chla", 0.0311278181792805, 0.000594175450783383, 52.3882602996143, 4.93281235468381e-67,      "Polar",
  "SPSG", "t_chla", 0.0676467149977894,  0.00461643829029263,  14.653442923744, 1.64755108560374e-06, "Equatorial",
  "WMED", "t_chla", 0.0359293074812375, 0.000954627809780489, 37.6369796826883, 1.88418982949485e-42,  "Temperate"
)

data$code <- factor(data$code, levels = c("ANTA", "SANT", "ARCT", "BPLR", "EMED", "WMED", "SPSG", "ARCH"))

# 计算标签y轴位置，避免遮挡柱子和误差线
label_y <- max(data$estimate + data$std.error) * 1.1

ggplot(data)+
  geom_bar(aes(y = estimate, x = code, fill = code), stat = "identity")+
  geom_errorbar(aes(ymin = estimate - std.error, ymax = estimate + std.error, x = code))+
  # 添加垂直分隔线
  geom_vline(xintercept = c(4.5, 6.5), linetype = "dashed", color = "gray60", linewidth = 0.8)+
  # 添加分组标签
  annotate("text", x = c(2.5, 5.5, 7.5), y = label_y, label = c("Polar", "Temperate", "Equatorial"), size = 4.5)+
  scale_fill_brewer(palette = "Set1", guide = "none")+
  theme_bw()+
  ylab("Specific absorption")+
  xlab("Oceanic province")+
  ggtitle("Specific absorption")

逻辑说明 #

ggplot中离散的x轴因子会被自动映射为从1开始的整数位置，你设置的code顺序对应位置1~8：

• BPLR是第4个位置、EMED是第5个位置，分界点为4.5；WMED是第6个位置、SPSG是第7个位置，分界点为6.5，传入geom_vline的xintercept参数即可添加分隔线
• 分组标签的x位置取对应分组的中点：Polar覆盖1_{4，中点为2.5；Temperate覆盖5}6，中点为5.5；Equatorial覆盖7~8，中点为7.5，y值可以根据展示需求自行调整高度
• 你可以修改linetype、color、size等参数自定义分隔线和标签的样式。

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