如何在ggplot2的scale_fill_discrete()函数中实现标签换行？

你可以通过两种方式给scale_fill_discrete()里的标签添加换行：

方法1：手动插入换行符\n #

直接在标签字符串中用\n指定需要换行的位置，ggplot会自动识别并拆分文本：

scale_fill_discrete(labels=c(
  "Is an inherited disorder,\nhaving genetic basis",
  "Due to\ndietary deficiency",
  "Term is known but\ndon’t know the etiology",
  "Completely unknown"
))

方法2：用stringr::str_wrap自动换行 #

如果不想手动控制换行位置，可以借助stringr包的str_wrap()函数，根据指定宽度自动拆分长文本。需要先加载stringr包：

library(stringr)

scale_fill_discrete(labels=str_wrap(c(
  "Is an inherited disorder, having genetic basis",
  "Due to dietary deficiency",
  "Term is known but don’t know the etiology",
  "Completely unknown"
), width = 20)) # 可根据需求调整width参数的数值

完整修改示例 #

结合你的代码，调整后的完整代码如下（两种方法二选一即可）：

library(ggplot2)
library(stringr) # 使用自动换行方法时需要加载

ggplot(dat, aes(x= What_is_NMD,  group=Gender, fill = What_is_NMD)) + 
  geom_bar(aes(y = ..prop.., fill = factor(..x..)), stat="count") +
  geom_text(aes(label = scales::percent(..prop.., accuracy = 0.01),
                y= ..prop.. ), stat= "count", vjust = -.5) +
  labs(x="What is NMD?", y = "Percent", fill="What is NMD?") +
  facet_grid(~Gender) +
  scale_y_continuous(labels = scales::percent)+
  theme(axis.text.x = element_blank(), 
        axis.ticks.x=element_blank(),
        legend.key.height=unit(1.5, "cm")) + # 适当调高图例高度适配换行标签
  # 手动换行写法
  scale_fill_discrete(labels=c(
    "Is an inherited disorder,\nhaving genetic basis",
    "Due to\ndietary deficiency",
    "Term is known but\ndon’t know the etiology",
    "Completely unknown"
  ))
  # 自动换行写法（替换上面的手动换行代码即可）
  # scale_fill_discrete(labels=str_wrap(c(
  #   "Is an inherited disorder, having genetic basis",
  #   "Due to dietary deficiency",
  #   "Term is known but don’t know the etiology",
  #   "Completely unknown"
  # ), width = 20))

另外注意：你原代码中fill = str_wrap(What_is_NMD)可以简化为fill = What_is_NMD，因为我们已经在scale_fill_discrete里单独设置了标签的换行，无需提前处理映射变量。

内容的提问来源于stack exchange，提问作者user149054