ggplot2复制编辑离散Y轴并添加右侧第二标签的实现方法

你可以通过构建SampleID到sampleName的一一映射向量，再搭配scale_y_discrete()的sec.axis参数实现需求，完整修改后的代码如下：

library(tidyverse)    

# 构建SampleID到sampleName的匹配映射，两种写法二选一即可
# 写法1：tidyverse风格
name_map <- deframe(ddff[, c("SampleID", "sampleName")])
# 写法2：基础R兼容写法
# name_map <- setNames(as.character(ddff$sampleName), as.character(ddff$SampleID))

ddff %>%
  ggplot(aes(x = Counts, y = SampleID)) +
  geom_point(aes(col = compartment), size = 4, alpha = 0.75) +
  geom_text(
    aes(label = paste0("   ", Counts)),
    size = 3,
    hjust = 0,
    nudge_x = -0.1,
    check_overlap = TRUE,
    color = "blue"
  ) +
  xlim(NA, 33000) +
  # 新增次Y轴配置
  scale_y_discrete(
    sec.axis = dup_axis(
      labels = name_map,
      name = "Sample Name"
    )
  ) +
  theme_light() +
  theme(plot.title = element_text(hjust = 0.5), aspect.ratio = 1) +
  theme(# 移除垂直网格线
    panel.grid.major.x = element_blank(),
    panel.grid.minor.x = element_blank()) +
  labs(title = "Library Size Overview",
       x = "Read Counts",
       y = "Sample ID",
       color = "Compartment") +
  theme(
    legend.position = c(.95, .95),
    legend.justification = c("right", "top"),
    legend.box.just = "right",
    legend.box.background = element_rect(color = "black", size = 1)
  )

补充说明 #

• dup_axis()会完全复制主Y轴的刻度位置，仅替换标签和轴名，保证两侧标签一一对应，不需要额外调整刻度位置
• 如果需要自定义右侧Y轴的文本样式，可以在theme()中新增对应参数调整，例如：

theme(
  # 调整右侧Y轴标签颜色、大小
  axis.text.y.right = element_text(color = "gray50", size = 9),
  # 调整右侧Y轴标题样式
  axis.title.y.right = element_text(color = "gray30", size = 10)
)

内容的提问来源于stack exchange，提问作者SteoG5972