删除ggraph中未使用的节点

Question

我有以下data.frame。

library(tidyverse)
library(ggraph)
library(tidygraph)
df <- structure(list(from = c(3L, 3L, 1L, 1L, 1L, 3L, 3L, 3L, 3L, 2L, 
2L, 1L, 3L, 1L, 3L, 3L, 3L, 1L, 3L, 3L, 2L, 3L, 3L, 2L, 3L, 3L, 
1L, 3L, 1L, 1L, 2L, 1L, 2L, 3L, 1L, 1L, 3L, 1L, 1L, 3L, 1L, 2L, 
3L, 3L, 3L, 3L, 3L, 1L, 1L, 3L, 1L, 3L, 3L, 3L, 3L, 1L, 2L, 1L, 
3L, 1L, 3L, 1L, 1L, 1L, 1L, 3L, 1L, 1L, 2L, 3L, 1L, 1L, 1L, 1L, 
1L, 1L, 3L, 3L, 2L, 3L, 3L, 1L, 3L, 1L, 1L, 1L, 1L, 1L, 3L, 3L, 
3L, 3L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 2L), to = c(31L, 21L, 5L, 
97L, 68L, 49L, 3L, 84L, 17L, 335L, 1L, 6L, 207L, 2L, 3L, 457L, 
3L, 149L, 17L, 3L, 41L, 126L, 89L, 150L, 42L, 262L, 235L, 79L, 
335L, 2L, 104L, 445L, 10L, 79L, 5L, 7L, 3L, 39L, 6L, 402L, 123L, 
104L, 246L, 448L, 261L, 44L, 47L, 170L, 158L, 435L, 39L, 47L, 
11L, 31L, 18L, 236L, 144L, 237L, 106L, 236L, 19L, 393L, 104L, 
6L, 440L, 191L, 171L, 302L, 255L, 134L, 197L, 373L, 68L, 10L, 
1L, 6L, 461L, 28L, 216L, 473L, 108L, 238L, 79L, 1L, 11L, 178L, 
432L, 5L, 3L, 91L, 449L, 26L, 123L, 456L, 73L, 1L, 105L, 432L, 
160L, 10L), time = c(2, 1, 3, 3, 1, 3, 1, 1, 1, 2, 3, 1, 1, 1, 
1, 3, 3, 2, 1, 1, 1, 3, 1, 1, 2, 2, 2, 3, 2, 1, 3, 3, 1, 3, 3, 
1, 2, 1, 1, 3, 3, 2, 2, 3, 3, 1, 1, 3, 1, 3, 1, 1, 1, 3, 3, 2, 
1, 3, 3, 2, 3, 3, 1, 1, 3, 1, 1, 3, 2, 3, 3, 3, 1, 2, 2, 2, 3, 
1, 1, 3, 1, 2, 3, 1, 1, 3, 3, 1, 3, 1, 3, 2, 3, 3, 2, 3, 1, 3, 
3, 1)), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, 
-100L))

g <- df %>% graph_from_data_frame()

然后此代码产生一个ggraph

g %>% 
  as_tbl_graph() %>% 
  activate(nodes) %>% 
  mutate(degree = centrality_degree()) %>% 
  ggraph()+
  geom_edge_fan(aes(color = time))+
  geom_node_point(aes(size = degree), 
                  show.legend = F)+
  coord_equal()+
  facet_edges(~time, drop = T)+
  theme_graph()

产生以下多面情节的情节：

我的问题是：如何删除图中各面中的无边节点，以使只有具有边的节点出现在每个面中？

谢谢！