堆叠柱状图x轴上下垂直文本放置优化方案咨询

针对堆叠柱状图x轴左侧垂直放置"Increasing/Decreasing"文本的需求，推荐使用归一化父坐标（NPC）逻辑固定文本位置，彻底避免annotate函数因数据范围变化导致的重叠或位置偏移问题。以下是3组覆盖不同数据场景的完整R代码：

测试用例1：正负数据均存在 #

library(ggplot2)

# 构造包含正负值的堆叠数据
df1 <- data.frame(
  category = rep(c("A", "B", "C"), each = 2),
  type = rep(c("Pos", "Neg"), 3),
  value = c(20, -15, 30, -25, 40, -30)
)

ggplot(df1, aes(x = category, y = value, fill = type)) +
  geom_col(position = "stack") +
  # 强制固定y轴范围为-50到50
  coord_cartesian(ylim = c(-50, 50)) +
  # 放置上方文本：Increasing
  geom_text(aes(x = -Inf, y = Inf, label = "Increasing"),
            hjust = 1.2, vjust = 1.2, angle = 90, size = 4,
            inherit.aes = FALSE, color = "darkgray") +
  # 放置下方文本：Decreasing
  geom_text(aes(x = -Inf, y = -Inf, label = "Decreasing"),
            hjust = 1.2, vjust = -0.2, angle = 90, size = 4,
            inherit.aes = FALSE, color = "darkgray") +
  theme_classic() +
  theme(axis.text.x = element_text(color = "gray"))

效果：文本分别固定在x轴左侧的上下方，与正负数据区域精准对应，无重叠问题。

测试用例2：仅存在正方向数据 #

# 构造只有正值的堆叠数据
df2 <- data.frame(
  category = rep(c("A", "B", "C"), each = 2),
  type = rep(c("Pos1", "Pos2"), 3),
  value = c(20, 15, 30, 10, 40, 5)
)

ggplot(df2, aes(x = category, y = value, fill = type)) +
  geom_col(position = "stack") +
  coord_cartesian(ylim = c(-50, 50)) +
  geom_text(aes(x = -Inf, y = Inf, label = "Increasing"),
            hjust = 1.2, vjust = 1.2, angle = 90, size = 4,
            inherit.aes = FALSE, color = "darkgray") +
  geom_text(aes(x = -Inf, y = -Inf, label = "Decreasing"),
            hjust = 1.2, vjust = -0.2, angle = 90, size = 4,
            inherit.aes = FALSE, color = "darkgray") +
  theme_classic() +
  theme(axis.text.x = element_text(color = "gray"))

效果：即使没有负数据，"Decreasing"依然固定在x轴左侧下方，位置不受数据范围影响。

测试用例3：仅存在负方向数据 #

# 构造只有负值的堆叠数据
df3 <- data.frame(
  category = rep(c("A", "B", "C"), each = 2),
  type = rep(c("Neg1", "Neg2"), 3),
  value = c(-20, -15, -30, -10, -40, -5)
)

ggplot(df3, aes(x = category, y = value, fill = type)) +
  geom_col(position = "stack") +
  coord_cartesian(ylim = c(-50, 50)) +
  geom_text(aes(x = -Inf, y = Inf, label = "Increasing"),
            hjust = 1.2, vjust = 1.2, angle = 90, size = 4,
            inherit.aes = FALSE, color = "darkgray") +
  geom_text(aes(x = -Inf, y = -Inf, label = "Decreasing"),
            hjust = 1.2, vjust = -0.2, angle = 90, size = 4,
            inherit.aes = FALSE, color = "darkgray") +
  theme_classic() +
  theme(axis.text.x = element_text(color = "gray"))

效果：即使没有正数据，"Increasing"依然固定在x轴左侧上方，位置稳定不偏移。

关键说明 #

• 使用x = -Inf定位到绘图区域最左侧，y = Inf/y = -Inf分别锚定顶部和底部，配合hjust/vjust微调文本与x轴的距离，避免重叠。
• coord_cartesian(ylim = c(-50, 50))强制锁定y轴范围，确保文本与x轴的相对位置始终一致。
• inherit.aes = FALSE避免继承全局美学映射，防止文本被错误绑定数据变量。

内容的提问来源于stack exchange，提问作者ixodid