如何在ggraph分面中仅保留各面板的关联节点？

问题根源在于facet_edges()仅对边进行分面过滤，不会自动过滤节点，因此所有节点会显示在每个面板中。以下是两种可行的解决方案：

方案一：拆分子图后用patchwork拼接（直观可靠） #

通过为每个分面分组单独生成子图，确保每个子图仅包含对应分组的边和关联节点，再拼接成整体图。

library(tidyverse)
library(tidygraph)
library(ggraph)
library(patchwork)

# 原始数据
myedges <- data.frame(from=rep(letters[1:5],2),
                      to=c(rep(LETTERS[12:13],2),
                      rep(LETTERS[14],3),
                      LETTERS[15:16], 
                      LETTERS[17]),
                      n_user=sample(1:20, 10, replace=TRUE),
                      f=rep(c("face_A", "face_B"),5)
                      ) 

# 按f分组拆分边数据
edge_groups <- split(myedges, myedges$f)

# 遍历每个分组生成对应绘图
plot_list <- map(edge_groups, function(edges) {
  # 提取当前分组的所有节点并计算n_user
  nodes <- edges %>% 
    pivot_longer(cols = c(from, to), names_to = "od", values_to = "node_name") %>% 
    group_by(node_name) %>% 
    summarise(n_user = sum(n_user), .groups = "drop")
  
  # 构建子图
  sub_graph <- tbl_graph(nodes = nodes, edges = edges)
  
  # 绘制弧图
  ggraph(sub_graph, layout = 'linear') + 
    geom_edge_arc(aes(edge_width=n_user, label=n_user), label_pos=0.1, edge_alpha=0.2)+
    geom_node_point(aes(size=n_user), alpha=0.5, show.legend = FALSE)+
    geom_node_text(aes(label = node_name), size=3, nudge_y = -0.5)+
    labs(title = unique(edges$f)) +
    theme_minimal()
})

# 拼接所有绘图（按列排列）
plot_list[[1]] + plot_list[[2]] + plot_layout(ncol = 1)

方案二：给节点添加分面标记，绘图时过滤节点（原生分面） #

通过给节点标记其所属的分面分组，在绘图时仅显示当前面板对应的节点，无需额外拼接工具。

library(tidyverse)
library(tidygraph)
library(ggraph)

# 原始数据
myedges <- data.frame(from=rep(letters[1:5],2),
                      to=c(rep(LETTERS[12:13],2),
                      rep(LETTERS[14],3),
                      LETTERS[15:16], 
                      LETTERS[17]),
                      n_user=sample(1:20, 10, replace=TRUE),
                      f=rep(c("face_A", "face_B"),5)
                      ) 

# 重新处理节点数据，标记每个节点出现的分面分组
mynodes <- myedges %>% 
  pivot_longer(cols = c(from, to), names_to = "od", values_to = "node_name") %>% 
  group_by(node_name) %>% 
  summarise(
    n_user = sum(n_user),
    # 记录节点所属的所有分面分组
    facets = list(unique(f))
  )

# 构建图对象
g <- tbl_graph(nodes = mynodes, edges = myedges)

# 绘图时过滤节点，仅显示当前面板对应的节点
ggraph(g, layout = 'linear') + 
  geom_edge_arc(aes(edge_width=n_user, label=n_user), label_pos=0.1, edge_alpha=0.2)+
  # 利用after_stat(panelvar1)获取当前面板的分面值，过滤节点
  geom_node_point(aes(size=n_user, filter = after_stat(panelvar1) %in% facets), 
                  alpha=0.5, show.legend = FALSE)+
  geom_node_text(aes(label = node_name, filter = after_stat(panelvar1) %in% facets), 
                 size=3, nudge_y = -0.5)+
  facet_edges(facets = vars(f), scales = "free") +
  theme_minimal()

内容的提问来源于stack exchange，提问作者maxbre