ggplot饼图：黑色分段的标签文字及填充色设为白色的需求

需求说明 #

• 除黑色填充的分段（low类）外，其余分段的标签文字颜色与对应分段的填充色保持一致；
• 黑色填充的分段，其标签文字及标签背景（内边距填充色）设置为白色，解决黑色标签文字无法看清的问题。

当前代码 #

ggplot(pigs2.proportions,
       aes(x="", y=comp_percent, fill = percent_class, width = 0.4)) +
  geom_bar(stat="identity") +
  geom_label(
    aes(
      label = ifelse(comp_percent %% 1 != 0, sprintf("%.2f%%", comp_percent),
                     sprintf("%.0f%%", comp_percent))),
            position = position_stack(vjust = 0.5), 
    size = 4,
    label.padding = unit(0.25, "lines"),
    show.legend = FALSE) +
  coord_polar("y", start=0) +
  facet_wrap(~factor(source, levels = c("fish", "soy", "skim")), labeller = custom_labeller("source")) +
  scale_fill_manual(values = c("low" = "black", "moderate" = "darkgray", "high" = "lightgray")) +
  theme(
    axis.text.x = element_blank(), # Hide labels on polar coordinate axis
    panel.grid = element_blank(),  # Remove grid lines
    panel.border = element_blank(),  # Remove round outline
    axis.text = element_blank(),  # Remove axis text
    axis.title = element_blank()  # Remove axis titles
  )

数据集结构 #

structure(list(source = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 3L, 
3L, 3L), levels = c("fish", "soy", "skim"), class = "factor"), 
    percent_class = structure(c(3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 
    2L), levels = c("low", "moderate", "high"), class = "factor"), 
    count = c(3L, 2L, 5L, 1L, 3L, 6L, 1L, 3L, 5L), comp_percent = c(30, 
    20, 50, 10, 30, 60, 11.1111111111111, 33.3333333333333, 55.5555555555556
    ), pos = c(15, 10, 25, 35, 35, 80, 45.5555555555556, 66.6666666666667, 
    137.777777777778)), class = c("grouped_df", "tbl_df", "tbl", 
"data.frame"), row.names = c(NA, -9L), groups = structure(list(
    percent_class = structure(1:3, levels = c("low", "moderate", 
    "high"), class = "factor"), .rows = structure(list(c(2L, 
    5L, 8L), c(3L, 6L, 9L), c(1L, 4L, 7L)), ptype = integer(0), class = c("vctrs_list_of", 
    "vctrs_vctr", "list"))), class = c("tbl_df", "tbl", "data.frame"
), row.names = c(NA, -3L), .drop = TRUE))

当前效果 #

修改后的代码及解释 #

# 定义颜色映射规则
fill_colors <- c("low" = "black", "moderate" = "darkgray", "high" = "lightgray")
text_colors <- ifelse(names(fill_colors) == "low", "white", fill_colors)
label_bg_colors <- ifelse(names(fill_colors) == "low", "white", NA)

ggplot(pigs2.proportions,
       aes(x="", y=comp_percent, fill = percent_class, width = 0.4)) +
  geom_bar(stat="identity") +
  geom_label(
    aes(
      label = ifelse(comp_percent %% 1 != 0, sprintf("%.2f%%", comp_percent),
                     sprintf("%.0f%%", comp_percent)),
      # 映射标签文字颜色与背景色
      color = percent_class,
      fill = percent_class
    ),
    position = position_stack(vjust = 0.5), 
    size = 4,
    label.padding = unit(0.25, "lines"),
    show.legend = FALSE) +
  coord_polar("y", start=0) +
  facet_wrap(~factor(source, levels = c("fish", "soy", "skim")), labeller = custom_labeller("source")) +
  # 配置各元素颜色刻度
  scale_fill_manual(values = fill_colors) +
  scale_color_manual(values = text_colors) +
  scale_fill_manual(values = label_bg_colors, na.value = "transparent", guide = "none") +
  theme(
    axis.text.x = element_blank(),
    panel.grid = element_blank(),
    panel.border = element_blank(),
    axis.text = element_blank(),
    axis.title = element_blank()
  )

关键改动说明 #

1. 颜色规则定义：针对不同分段类，分别指定饼图填充色、标签文字色、标签背景色，其中low类单独设置白色文字和白色背景；
2. 标签属性映射：在geom_label的aes中新增color和fill映射，分别控制标签文字和标签背景的颜色；
3. 刻度配置：通过三个scale_*_manual分别设置饼图填充色、标签文字色、标签背景色，非low类的标签背景设为透明，避免遮挡饼图本身的填充色。

内容的提问来源于stack exchange，提问作者Joe