ggplot2分面图轴标签调整：移除首分面标签并居中

以下是修改后的代码，可实现你想要的效果：

library(ggplot2)
library(ggh4x)

data <- data.frame(group = c("Group 1", "Group 1", "Group 2", "Group 2", "Group 1", "Group 1", "Group 2", "Group 2", "Group 1", "Group 1", "Group 2", "Group 2"),
                   administered = c("no", "yes", "no", "yes", "no", "yes", "no", "yes", "no", "yes", "no", "yes"),
                   medication = c("DRUG A with a long name", "DRUG A with a long name", "DRUG A with a long name", "DRUG A with a long name", "DRUG B", "DRUG B", "DRUG B", "DRUG B", "DRUG C", "DRUG C", "DRUG C", "DRUG C"),
                   count = c(100,200,50,88,99,300,77,45,12,0,9,27))

ggplot(data, aes(x = medication,
                 y = count,
                 fill = administered)) +
  geom_col(position = "fill") +
  ylab("proportion") +    
  scale_fill_manual(values = c("no"="#FF0000FF",
                               "yes"="#0000FFFF"))+
  theme(axis.ticks.y = element_blank(),
        # 隐藏原有分面标签及背景
        strip.text = element_blank(),
        strip.background = element_blank()) +
  facet_wrap2(~ group, scales = "free") +
  facetted_pos_scales(y = list(
    scale_y_reverse(labels = scales::percent),
    scale_y_continuous(labels = scales::percent))) +
  coord_flip() +
  # 给指定分面添加顶部居中标签
  annotate_outside("text", label = "Group 1", 
                   x = 0.5, y = Inf, vjust = 1.2,
                   facet = ~ group == "Group 1") +
  annotate_outside("text", label = "Group 2", 
                   x = 0.5, y = Inf, vjust = 1.2,
                   facet = ~ group == "Group 2")

关键修改说明： #

• 移除默认分面标签：通过theme设置strip.text = element_blank()隐藏原有标签，strip.background = element_blank()去掉分面标签的背景框
• 添加自定义居中标签：利用ggh4x的annotate_outside函数，精准指定标签所属的分面（通过facet参数），x=0.5保证标签在分面水平居中，y=Inf定位到分面顶部，vjust=1.2微调文本位置，避免与绘图区域重叠

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