ggplot2,在轴标签内的下标中获取 % 符号

ggplot2, getting a % symbol in subscript within axis labels

我正在尝试在轴中获取一个 % 符号作为下标。通常,使用表达式和方括号 [] 可以获得下标。但是当我收到错误时,符号似乎无法正确解析。有谁知道如何修复或变通?比如下面的下标要%怎么办:

library(tidyverse)
  
iris %>% ggplot(aes(x = Sepal.Length, y = Sepal.Width)) + 
  geom_point(aes(colour = Species)) + 
  geom_smooth(method = loess) + 
  labs(y = expression(Blah[1*d]*"%"))

%符号在括号中移动时

iris %>% ggplot(aes(x = Sepal.Length, y = Sepal.Width)) + 
  geom_point(aes(colour = Species)) + 
  geom_smooth(method = loess) + 
  labs(y = expression(Blah[1d%]))

出现以下错误消息:

Error: unexpected symbol in: " geom_smooth(method = loess) +
labs(y = expression(Blah[1d"

移动方括号中的 % 符号并使用引号"" 删除错误消息

iris %>% ggplot(aes(x = Sepal.Length, y = Sepal.Width)) + 
  geom_point(aes(colour = Species)) + 
  geom_smooth(method = loess) + 
  labs(y = expression(Blah["1d%"]))

并生成此图: