如何为ggplot2的facet_grid分面图添加分面之间的虚线分隔线

解决方案 #

你可以借助ggh4x扩展包的facet_grid2()功能实现需求，它原生支持自定义分面分隔线样式，不需要手动计算坐标或修改底层绘图对象，代码修改成本极低。

完整可运行代码

如果未安装ggh4x先执行安装命令：
install.packages("ggh4x")

绘图代码：

library(ggplot2)
library(ggstance)
library(ggh4x)

# 数据集和原有逻辑保持一致
data_people <- data.frame(Group = c("Good", "Medium", "Medium", "Medium", "Medium",  "BAD", "BAD", "BAD", "BAD"),
                          people = c("Jonney", "Eva", "Eilse", "Doe", "Matt", "June", "Som", "Clara","Nick"),
                          number = c(0.04, 0.09, 0.10, 0.13, 0.13, 0.06, 0.05, 0.00, 0.3))

ggplot(data = data_people, aes(x = number, y = people, group = Group)) +
  geom_barh(stat = "identity", colour = "black") + 
  scale_x_continuous(breaks = c(-0.20, 0.00, 0.20, 0.40, 0.60, 0.80, 1.00),
                     limits = c(-0.20, 1)) +
  # 替换原有facet_grid，添加分面分隔线配置
  facet_grid2(Group~., scales = "free_y", space = "free_y", switch = 'y',
              panel.lines = element_line(linetype = "dashed", color = "black", linewidth = 0.5)) +
  # 可调整分面间距让分隔线显示更清晰
  theme(panel.spacing.y = unit(0.5, "lines")) +
  xlab(" ") +
  ylab(" ")

运行上述代码即可得到分面之间带虚线分隔的预期效果，你可以通过修改element_line内的参数自定义虚线的颜色、粗细、虚实程度。

内容的提问来源于stack exchange，提问作者Saw Simeon