r - 节点不尊重 ggraph/igraph 中的分面

Question

我在理解 ggplot2 和 ggraph 在分面方面的区别时遇到了一些困难。考虑以下数据:

library(igraph)
library(ggraph)
library(ggplot2)

df <- structure(list(x = c("H001", "H024", "H090", "H090", "H098", 
                     "H103", "H126", "H152", "H155", "H155", "B002", "B011", "B075", 
                     "B092", "M002", "M002", "M002", "M050", "M050", "M085", "M085", 
                     "M247", "M247", "M247"), 
               y = c("H103", "H126", "H152", "H155","H155", "H001", "H024", "H090", "H090", "H098", "B092", "B075", 
                      "B011", "B002", "M050", "M085", "M247", "M002", "M247", "M002", "M247", "M002", "M050", "M085"), 
               r = c(0.963248925980302, 0.991452643542894, 0.965947578382865, 
                     0.963234153063794, 0.962277411462605, 0.963248925980302, 
                     0.991452643542894, 0.965947578382865, 0.963234153063794, 
                     0.962277411462605, 0.960948147492217, 0.957371360458182, 
                     0.957371360458182, 0.960948147492217, 0.96976135236222, 
                     0.977435712803837, 0.997037031981303, 0.96976135236222, 
                     0.978553503235858, 0.977435712803837, 0.992741796542001, 
                     0.997037031981303, 0.978553503235858, 0.992741796542001), 
               facet_var = c("08MH", "08MH", "08MH", "08MH", "08MH", "08MH", "08MH", "08MH", "08MH", 
                             "08MH", "08HB", "08HB", "08HB", "08HB", "08NM", "08NM", "08NM", "08NM", 
                             "08NM", "08NM", "08NM", "08NM", "08NM", "08NM")), 
          class = "data.frame", row.names = c(NA, -24L), .Names = c("x", "y", "r", "facet_var")
)

如果我使用简单的 ggplot 绘制数据，我可以以我认为“正常”的方式进行分面:

ggplot(df, aes(x = x, y = y)) +
         geom_point() +
         facet_wrap(~facet_var)

也就是说，facet_var 的每个级别都有一些与之关联的点，并且只有这些点才会绘制在相应的方面中。现在，如果我使用 ggraph 尝试类似的方法，我会遇到对我来说很奇怪的行为(尽管我显然承认这只是反射(reflect)了缺乏理解):

graph_cors <- graph_from_data_frame(df, directed = FALSE)

ggraph(graph_cors) +
  geom_edge_link(aes(edge_alpha = abs(r), color = r), edge_width = 2) +
  guides(edge_alpha = "none") +
  scale_edge_colour_gradientn(limits = c(-1, 1), colors = topo.colors(5)) +
  geom_node_point(color = "black", size = 5) +
  geom_node_text(aes(label = name), repel = TRUE) +
  facet_edges(~facet_var)

尽管边尊重分面，但所有节点都绘制在每个分面上。谁能概述一下我在这里做错了什么？

session 信息

> sessionInfo()
R version 3.4.2 (2017-09-28)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

Matrix products: default

locale:
[1] LC_COLLATE=English_Canada.1252  LC_CTYPE=English_Canada.1252    LC_MONETARY=English_Canada.1252 LC_NUMERIC=C                   
[5] LC_TIME=English_Canada.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] ggraph_1.0.0    ggplot2_2.2.1   igraph_1.1.2    testthat_1.0.2  devtools_1.13.3

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.13          compiler_3.4.2        plyr_1.8.4            bindr_0.1             viridis_0.4.0        
 [6] tools_3.4.2           digest_0.6.12         viridisLite_0.2.0     memoise_1.1.0         tibble_1.3.4         
[11] gtable_0.2.0          pkgconfig_2.0.1       rlang_0.1.2           rstudioapi_0.7.0-9000 ggrepel_0.7.0        
[16] yaml_2.1.14           bindrcpp_0.2          gridExtra_2.3         withr_2.0.0           dplyr_0.7.4          
[21] grid_3.4.2            glue_1.1.1            R6_2.2.2              tweenr_0.1.5          udunits2_0.13        
[26] magrittr_1.5          scales_0.5.0          fortunes_1.5-4        MASS_7.3-47           units_0.4-6          
[31] assertthat_0.2.0      swtext_0.0.1          ggforce_0.1.1         colorspace_1.3-2      lazyeval_0.2.0       
[36] munsell_0.4.3         crayon_1.3.4    

Answer 1

您需要将相关变量作为节点属性分配给节点的facet。你的facet_var变量是一个边缘属性；如果将其作为节点属性分配给每个二元组中的每个节点，则分面将起作用。

facet_graph 由两个变量组成的分面(例如边属性和节点属性)。似乎 facet_nodes 就是您想要的，但您需要向参数发送节点属性，而不是边缘属性。

目前，您的 igraph 对象仅具有边缘属性:

> graph_cors
IGRAPH UN-- 16 24 -- 
+ attr: name (v/c), r (e/n), facet_var (e/c)
+ edges (vertex names):
 [1] H001--H103 H024--H126 H090--H152 H090--H155 H098--H155 H001--H103 H024--H126 H090--H152
 [9] H090--H155 H098--H155 B002--B092 B011--B075 B011--B075 B002--B092 M002--M050 M002--M085
[17] M002--M247 M002--M050 M050--M247 M002--M085 M085--M247 M002--M247 M050--M247 M085--M247

graph_cors <- graph_from_data_frame(df, directed = FALSE)

facet_nodes <- cbind(c(df[,1], df[,2]), 
                     df[match(c(df[,1], df[,2]), df[,1]),4])

# Assign the facet_var variable to corresponding dyad pairs
V(graph_cors)$facet_node <- facet_nodes[match(V(graph_cors)$name, facet_nodes[,1]),2]

现在，igraph 对象有一个节点属性(“facet_node”):

> graph_cors
IGRAPH UN-- 16 24 -- 
+ attr: name (v/c), facet_node (v/c), r (e/n), facet_var (e/c)
+ edges (vertex names):
 [1] H001--H103 H024--H126 H090--H152 H090--H155 H098--H155 H001--H103 H024--H126 H090--H152
 [9] H090--H155 H098--H155 B002--B092 B011--B075 B011--B075 B002--B092 M002--M050 M002--M085
[17] M002--M247 M002--M050 M050--M247 M002--M085 M085--M247 M002--M247 M050--M247 M085--M247

# Use the facet_nodes argument with the nodal attribute
ggraph(graph_cors) +
  geom_edge_link(aes(edge_alpha = abs(r), color = r), edge_width = 2) +
  guides(edge_alpha = "none") +
  scale_edge_colour_gradientn(limits = c(-1, 1), colors = topo.colors(5)) +
  geom_node_point(color = "black", size = 5) +
  geom_node_text(aes(label = name), repel = TRUE) +
  facet_nodes(~facet_node)