环形柱状图中为负值设置不同填充颜色的实现方案

要实现以0为分界，将负值柱子设为蓝色、正值保留原色系的效果，核心是基于柱子数值的正负创建分组变量，再通过手动颜色映射实现区分。以下是修改后的完整代码：

数据准备（不变） #

uni_data <- structure(list(from = c("Argentina", "Canada", "China", "Germany", 
"Malawi", "Mexico", "Poland", "Russia", "South Africa", "United Republic of Tanzania", 
"United States", "Zambia"), to = c("Zimbabwe", "Zimbabwe", "Zimbabwe", 
"Zimbabwe", "Zimbabwe", "Zimbabwe", "Zimbabwe", "Zimbabwe", "Zimbabwe", 
"Zimbabwe", "Zimbabwe", "Zimbabwe"), fraction_mean = c(-1.16218764988057, 
0.556848791658583, -0.785724007068475, -0.668776616353553, 2.98715326478044, 
0.632802483886891, -0.952039672216194, -0.275904847337713, 1.91885749928563, 
2.18477200782915, -1.22917889731657, 4.4028142502411), d_long = c(0.124, 
0.2794, 0.2466, 0.0785, 2.8646, 0.202, 0.1153, 0.1238, 0.2247, 
1.6428, 0.1664, 2.3044), mean_exposure = c(0.219336124378027, 
0.964248264036473, -0.833368763174394, -0.520689933363188, 1.45247015618433, 
-1.53268987398912, -1.15713981781644, 0.791178790005572, 0.482041972598713, 
2.02018800214932, 1.40628459671399, 2.61998072810955)), row.names = c(1L, 
5L, 6L, 9L, 14L, 15L, 17L, 19L, 22L, 25L, 26L, 27L), class = "data.frame")

修改后的绘图代码 #

library(tidyverse)

plot_uni <- uni_data %>%
  group_by(from) %>%
  summarise(
    sum_length = fraction_mean,
    mean_exposure = mean_exposure,
    delta = d_long
  ) %>%
  mutate(
    mean_exposure = round(mean_exposure, digits = 0),
    # 新增：根据sum_length正负创建分组变量
    fill_group = ifelse(sum_length < 0, "负值", "正值")
  )

plt2 <- ggplot(plot_uni) +
  geom_col(
    aes(
      x = reorder(str_wrap(from, 5), sum_length),
      y = sum_length,
      fill = fill_group  # 映射到新的分组变量
    ),
    position = "dodge2",
    show.legend = TRUE,
    alpha = .9
  ) +
  geom_point(
    aes(
      x = reorder(str_wrap(from, 5),sum_length),
      y = mean_exposure
    ),
    size = 3,
    color = "gray12"
  ) +
  geom_segment(
    aes(
      x = reorder(str_wrap(from, 5), sum_length),
      y = 0,
      xend = reorder(str_wrap(from, 5), sum_length),
      yend = 6
    ),
    linetype = "dashed",
    color = "gray12"
  ) + 
  coord_polar() + 
  labs(x=" ", y=" ")

plt3 <- plt2 +
  scale_y_continuous(
    limits = c(-1, 6),
    expand = c(0, 0),
    breaks = c(0,2, 3, 4)
  ) + 
  # 手动指定颜色：负值设为蓝色，正值保留原紫粉色系
  scale_fill_manual(
    "数值类型",
    values = c(
      "负值" = "#1f77b4",  # 蓝色，可自行替换为喜欢的蓝色系代码
      "正值" = "#C06C84"   # 原色系中的紫色，若要保留渐变可调整为scale_fill_gradientn结合分组
    )
  ) +
  guides(
    fill = guide_legend(title.position = "top", title.hjust = .5)
  ) +
  theme(
    axis.title = element_blank(),
    axis.ticks = element_blank(),
    axis.text.y = element_blank(),
    axis.text.x = element_text(color = "gray12", size = 10),
    legend.position = "bottom",
  )

plt3

关键修改说明 #

1. 新增分组变量：在plot_uni数据处理中添加fill_group，通过ifelse判断sum_length是否小于0，将柱子分为正负两组。
2. 调整填充映射：将geom_col的fill参数从原delta改为新的fill_group，实现按正负值区分颜色。
3. 手动颜色设置：用scale_fill_manual直接指定负值为蓝色、正值为原色系颜色，替代原有的渐变填充。如果需要保留正值的渐变效果，可以结合fill_group和delta做分层映射，或者使用scale_fill_gradientn设置断点在0处。

内容的提问来源于stack exchange，提问作者MoonS