在ggplot多系列条形图中按条件为不合格条形添加阴影

没问题，这事儿好办！咱们可以通过给数据加个标记列，再结合ggplot的图层叠加来实现你要的阴影标记效果，下面是具体的步骤和代码，直接就能用：

1. 预处理数据，添加标记列 #

首先咱们先把示例数据加载进来，然后新增一个flag列，专门用来标记哪些条形需要加阴影——也就是满足CV>20或者Sample_size<30的行：

library(tidyverse)

# 你的示例数据
df <- structure(list(Group = c("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J"), Perc = c(38, 38, 46, 27, 18, 39, 43, 27, 38, 40, 39, 39, 50, 32, 33, 41, 52, 32, 43, 43), Lower_CI = c(36, 36, 36, 15, 8, 31, 30, 14, 18, 23, 38, 37, 40, 21, 15, 31, 40, 17, 24, 27), Upper_CI = c(39, 40, 57, 39, 27, 47, 55, 40, 58, 56, 41, 41, 60, 44, 51, 51, 64, 47, 63, 60), CV = c(2, 2, 11, 12, 28, 11, 15, 6, 18, 13, 2, 2, 10, 19, 5, 13, 12, 23, 14, 20), Sample_size = c(30, 15, 140, 40, 69, 75, 56, 256, 45, 536, 4852, 785, 36, 48, 315, 120, 83, 15, 123, 45), Period = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2)), row.names = c(NA, -20L), class = c("tbl_df", "tbl", "data.frame"))

# 添加标记列：符合条件的标记为TRUE
df <- df %>%
  mutate(flag = CV > 20 | Sample_size < 30)

2. 绘制带阴影标记的条形图 #

这里提供两种实现方式，你可以根据自己的需求选：

方式一：灰色半透明背景阴影 #

用geom_rect给需要标记的条形添加灰色背景，放在条形图层的下方，效果自然：

ggplot(df, aes(x = Group, y = Perc, fill = factor(Period))) +
  # 先画阴影背景：只给flag为TRUE的条形添加
  geom_rect(
    data = df %>% filter(flag),
    aes(xmin = as.numeric(Group) - 0.3, xmax = as.numeric(Group) + 0.3,
        ymin = 0, ymax = max(df$Upper_CI) * 1.05),  # ymax设为比最大置信上限稍高一点，避免截断
    fill = "gray80", alpha = 0.3
  ) +
  # 绘制分组条形
  geom_col(position = position_dodge(width = 0.6), width = 0.5) +
  # 添加置信区间误差线
  geom_errorbar(aes(ymin = Lower_CI, ymax = Upper_CI),
                position = position_dodge(width = 0.6), width = 0.2) +
  # 调整标签和主题
  labs(title = "不同Period下各组百分比差异",
       x = "组别", y = "百分比", fill = "时期") +
  theme_minimal() +
  theme(plot.title = element_text(hjust = 0.5))

方式二：斜线填充阴影（更贴近Excel示例） #

如果想要和Excel示例一样的斜线阴影，可以用ggpattern包来实现，先安装这个包，然后用带图案的条形：

# 先安装包（第一次用需要安装）
# install.packages("ggpattern")
library(ggpattern)

ggplot(df, aes(x = Group, y = Perc, fill = factor(Period))) +
  # 带图案的条形：只有flag为TRUE的才显示斜线
  geom_col_pattern(
    aes(pattern = flag),
    position = position_dodge(width = 0.6), width = 0.5,
    pattern_fill = "gray50", pattern_density = 0.05, pattern_spacing = 0.02
  ) +
  # 添加误差线
  geom_errorbar(aes(ymin = Lower_CI, ymax = Upper_CI),
                position = position_dodge(width = 0.6), width = 0.2) +
  # 调整标签和主题
  labs(title = "不同Period下各组百分比差异",
       x = "组别", y = "百分比", fill = "时期", pattern = "标记项") +
  theme_minimal() +
  theme(plot.title = element_text(hjust = 0.5)) +
  # 手动设置图案：未标记的无图案，标记的用斜线
  scale_pattern_manual(values = c(FALSE = "none", TRUE = "stripe"))

内容的提问来源于stack exchange，提问作者barnesybee