如何在R中用ggforce实现嵌套圆切片、上色及文本调整？

需求说明 #

已有基于ggforce的嵌套圆形调查进度图，需要实现：

• 将最内层圆形分割为3个扇形切片，分别为Group A（红色）、Group B（绿色）、Group C（黄色）上色
• 优化切片内文本的位置，使其更居中美观

关键修改步骤 #

1. 修正角度计算逻辑
   原代码中角度计算使用了不合理系数（如1.4*pi、8*pi），需改为按分组数量占总响应数的比例分配完整的2*pi圆周角度，确保扇形比例准确。

2. 添加扇形填充层
   使用ggforce::geom_arc_bar绘制带填充色的扇形切片，替代原有的仅线段分割，通过start和end参数定义每个扇形的角度范围，绑定分组对应的填充色。

3. 优化文本位置计算
   调整文本距离中心的半径比例，同时根据中点角度的正负修正Y轴方向，确保文本始终在扇形内部居中显示。

4. 统一颜色映射
   为三个分组指定目标颜色，在scale_fill_manual中明确对应关系，避免颜色混乱。

修改后的完整代码 #

total_participants = 7500  
undelivered = 2500
total_invited = 5000  
total_responses = 2000  
total_unanswered = 1100  
group_c = 900 
group_a = 650  
group_b = 450 
partially_completed = 300  
library(ggplot2)
library(ggforce)

# Define total responses in the pie chart
total_count = group_a + group_b + group_c

# 修正角度计算：按比例分配2π圆周
angle_a = 2 * pi * (group_a / total_count)  
angle_b = 2 * pi * (group_b / total_count)  
angle_c = 2 * pi - (angle_a + angle_b)  

# Cumulative angles for the pie slices
angles = c(0, angle_a, angle_a + angle_b, 2 * pi)

# Midpoint angles for text placement
mid_angles = c((angles[1] + angles[2]) / 2,  
               (angles[2] + angles[3]) / 2,  
               (angles[3] + angles[4]) / 2) 

# Pie chart position and radius
pie_center_x = 2.7
pie_center_y = -0.6
pie_radius = 3

# Data frame for the pie chart
pie_data = data.frame(
  category = c("Group A", "Group B", "Group C"),
  value = c(group_a, group_b + total_unanswered, group_c),
  start = angles[1:3],
  end = angles[2:4],
  mid_angle = mid_angles,
  x_start = pie_center_x,
  y_start = pie_center_y,
  # 优化文本位置：调整半径比例，根据角度修正Y方向
  text_x = pie_center_x + (pie_radius * 0.5) * cos(mid_angles),
  text_y = pie_center_y + (pie_radius * 0.5) * sin(mid_angles) * ifelse(mid_angles > pi, -1, 1)
)

# Bubble chart data
bubble_data = data.frame(
  group = c(paste0("Total Participants: ", total_participants),
            paste0("Invited: ", total_invited),
            paste0("Responded: ", total_unanswered + group_a + group_b + group_c),
            paste0("Not Delivered: ", undelivered),
            paste0("Partial Responses: ", partially_completed)),
  radius = c(7, 5, 3, 0.8, 0.8),
  x0 = c(0, 1, 2.7, -5.4, -1),
  y0 = c(0, 0, -0.6, 1, 1.4)
)

# Final plot
plot_bubble_pie = ggplot() +
  
  # Bubble chart
  ggforce::geom_circle(data = bubble_data, aes(x0 = x0, y0 = y0, r = radius, 
                                               fill = factor(group, group)), 
                       alpha = 1) +
  geom_text(data = bubble_data, aes(x = x0, y = y0 + radius + 0.2, label = group), 
            size = 3.2, fontface = "bold") +
  
  # 添加扇形填充层
  ggforce::geom_arc_bar(data = pie_data,
                        aes(x0 = x_start, y0 = y_start, r0 = 0, r = pie_radius,
                            start = start, end = end, fill = category),
                        color = "black", linewidth = 1) +
  
  # Labels inside pie slices（合并分组名和数值）
  geom_label(data = pie_data, 
             aes(x = text_x, y = text_y, label = paste0(category, ":\n", value)), 
             size = 3.2, fontface = "bold", label.size = 0, fill = NA) +
  
  # 自定义颜色映射：对应需求的红、绿、黄
  scale_fill_manual(values = c("Group A" = "#e74c3c", 
                               "Group B" = "#2ecc71", 
                               "Group C" = "#f1c40f",
                               '#77bca2', '#e1926b', '#a09cc8', "grey", "orange"),
                    guide = 'none') +
  
  coord_equal() +
  theme_void()

# Display the plot
plot_bubble_pie

代码说明 #

• 角度计算：删除错误系数，改为基于2*pi的比例分配，保证扇形占比准确
• 扇形绘制：使用geom_arc_bar实现填充，r0=0表示从中心开始绘制完整扇形
• 文本位置：调整距离中心的比例为0.5倍半径，通过ifelse修正下半圆文本的Y轴方向，避免偏移出扇形
• 颜色映射：明确指定三个分组的颜色，同时保留原有嵌套圆形的颜色配置

内容的提问来源于stack exchange，提问作者Homer Jay Simpson