使用包含下标字符的命名向量重命名 ggplot x 轴标签

Question

我想用命名向量替换图中的 x 轴标签。我想在一些新名称中添加下标字符。我在下面给出了一个示例，其中我希望“H2O2 500 µM”为“H₂O₂ 500 µM”。

我读过这可以通过将替换文本包含在

expression()

中来完成，但是当使用命名向量来替换名称时，这似乎不起作用。

这是一个简化的演示。

demo_data <- structure(list(treatment_duration_weeks = c(9, 9, 9, 9, 9, 9, 
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 15, 15, 15, 15, 15, 15, 15, 
15, 15, 15, 15, 15), treatment = c("negative_control", "negative_control", 
"negative_control", "treatment1", "treatment1", "treatment1", 
"treatment2", "treatment2", "treatment2", "treatment3", "treatment3", 
"treatment3", "treatment4", "treatment4", "treatment4", "H2O2-500uM", 
"H2O2-500uM", "H2O2-500uM", "negative_control", "negative_control", 
"treatment1", "treatment1", "treatment2", "treatment2", "treatment3", 
"treatment3", "treatment4", "treatment4", "H2O2-500uM", "H2O2-500uM"
), level = c(100, 100, 100, 107, 148, 126, 112, 160, 131, 112, 
159, 122, 113, 170, 130, 54, 64, 24, 101, 100, 105, 190, 96, 
170, 84, 176, 98, 171, 53, 59)), row.names = c(NA, -30L), class = c("tbl_df", 
"tbl", "data.frame"))


treatment_rename <- c("negative_control" = "NC",
                      "treatment1" = "Treatment 1",
                      "treatment2" = "Treatment 2",
                      "treatment3" = "Treatment 3",
                      "treatment4" = "Treatment 4",
                      "H2O2-500uM" = "H2O2 500 µM")

ggplot(demo_data, aes(x = treatment, y = level)) +
  facet_wrap(~ treatment_duration_weeks) +
  stat_summary(aes(fill = treatment),
               fun = mean, colour = "black", geom = "bar") +
  geom_jitter(aes(fill = treatment),
              shape = 21, colour = "black", 
              width = 0.1, height = 0, 
              size = 3) +
  stat_summary(fun.data = mean_se,  
               geom = "errorbar", width = 0.2) +
  scale_x_discrete(labels = treatment_rename) +
  theme_bw() +
  theme(axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1),
        legend.position = "none")

我已经尝试过类似的帖子，但无法使其正常工作。

如何给x轴刻度标签添加下标

Answer 1

一种选择是使用

scales::label_parse()

，这当然仍然需要创建正确的数学表达式的向量：

library(ggplot2)

treatment_rename <- c(
  "negative_control" = "NC",
  "treatment1" = "Treatment~1",
  "treatment2" = "Treatment~2",
  "treatment3" = "Treatment~3",
  "treatment4" = "Treatment~4",
  "H2O2-500uM" = "H[2]*O[2]~500~µM"
)

ggplot(demo_data, aes(x = treatment, y = level)) +
  facet_wrap(~treatment_duration_weeks) +
  stat_summary(aes(fill = treatment),
    fun = mean, colour = "black", geom = "bar"
  ) +
  geom_jitter(aes(fill = treatment),
    shape = 21, colour = "black",
    width = 0.1, height = 0,
    size = 3
  ) +
  stat_summary(
    fun.data = mean_se,
    geom = "errorbar", width = 0.2
  ) +
  scale_x_discrete(labels = \(x) scales::label_parse()(treatment_rename[x])) +
  theme_bw() +
  theme(
    axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1),
    legend.position = "none"
  )

第二个选择是使用 unicode 下标：

treatment_rename <- c(
  "negative_control" = "NC",
  "treatment1" = "Treatment 1",
  "treatment2" = "Treatment 2",
  "treatment3" = "Treatment 3",
  "treatment4" = "Treatment 4",
  "H2O2-500uM" = "H\u2082O\u2082 500 µM"
)

ggplot(demo_data, aes(x = treatment, y = level)) +
  facet_wrap(~treatment_duration_weeks) +
  stat_summary(aes(fill = treatment),
               fun = mean, colour = "black", geom = "bar"
  ) +
  geom_jitter(aes(fill = treatment),
              shape = 21, colour = "black",
              width = 0.1, height = 0,
              size = 3
  ) +
  stat_summary(
    fun.data = mean_se,
    geom = "errorbar", width = 0.2
  ) +
  scale_x_discrete(labels = treatment_rename) +
  theme_bw() +
  theme(
    axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1),
    legend.position = "none"
  )