如何在ggplot翻转坐标系的柱状图中添加多组Y轴文本？

需求说明 #

• 当前绘图：横向渐变填充柱状图，仅展示类别名称与对应柱子
• 目标效果：在每个柱子的对应位置添加1-2组额外文本系列，实现类似多列信息对齐展示的横向条形图效果

当前绘图代码 #

ggplot() + geom_col(data = s, aes(x = V1, y = V3, fill = V3), show.legend = F) + 
coord_flip() + 
labs(x = "", y = "") + 
scale_fill_gradient(low = "yellow", high="darkgreen") + 
theme(axis.text.y = element_text(vjust = 0, hjust = 0), plot.margin = margin(1, 0.3, 0.1, 0.3, "cm"), panel.background = element_rect(fill = 'white', colour = 'white'), axis.ticks.y = element_blank()) + ylim(0, 6)

数据说明 #

模拟数据 #

1  a  b  6  7
2  c  d  8  9
3  g  f  5  4
4  f  n  3  2

真实数据结构 #

structure(list(V1 = c("regulation of locomotion", "regulation of cell migration", 
"skin development", "negative regulation of biological process", 
"cell adhesion", "response to oxygen-containing compound"), V2 = c(7.74e-05, 
0.000143, 0.000165, 0.000176, 0.00019, 0.00019), V3 = c(4.111259039, 
3.844663963, 3.782516056, 3.754487332, 3.721246399, 3.721246399
)), row.names = c(NA, 6L), class = "data.frame")

解决方案：完全可以用ggplot实现 #

核心思路是通过geom_text()在指定位置添加文本系列，结合坐标调整实现对齐。以下是基于真实数据的示例代码：

实现代码 #

library(ggplot2)

# 加载真实数据
s <- structure(list(V1 = c("regulation of locomotion", "regulation of cell migration", 
"skin development", "negative regulation of biological process", 
"cell adhesion", "response to oxygen-containing compound"), V2 = c(7.74e-05, 
0.000143, 0.000165, 0.000176, 0.00019, 0.00019), V3 = c(4.111259039, 
3.844663963, 3.782516056, 3.754487332, 3.721246399, 3.721246399
)), row.names = c(NA, 6L), class = "data.frame")

ggplot(s, aes(x = V1, y = V3)) +
  geom_col(aes(fill = V3), show.legend = F) +
  # 添加第一组文本（V2，格式化科学计数法）
  geom_text(aes(y = 6.2, label = sprintf("%.1e", V2)), hjust = 0, size = 3.5) +
  # 若需第二组文本，复制该行并调整y值即可
  # geom_text(aes(y = 6.8, label = "自定义文本"), hjust = 0, size = 3.5) +
  coord_flip() +
  labs(x = "", y = "") +
  scale_fill_gradient(low = "yellow", high="darkgreen") +
  theme(
    axis.text.y = element_text(vjust = 0, hjust = 0),
    plot.margin = margin(1, 2, 0.1, 0.3, "cm"), # 加大右侧边距避免文本截断
    panel.background = element_rect(fill = 'white', colour = 'white'),
    axis.ticks.y = element_blank()
  ) +
  ylim(0, 7) # 扩大y轴范围预留文本空间

关键要点 #

• 通过调整geom_text()的y参数（coord_flip()后对应横向位置）控制文本的左右排列
• 多组文本通过多次调用geom_text()，设置不同y值实现分层
• 若需要更复杂的文本样式（如背景、换行），可替换为ggtext::geom_richtext()

内容的提问来源于stack exchange，提问作者Amir Valizadeh