R：修改图表答案

【问题标题】：R: Modifying GraphsR：修改图表
【发布时间】：2020-12-11 20:20:38
【问题描述】：

我在这里发布了对另一个 stackoverflow 帖子的评论/回复：R: Understanding Graph 与 R 中的图形有关。

如果你创建一些与电影和演员对应的数据（其中电影不能直接连接到其他电影，演员不能直接连接到其他演员），你写一些 R 代码来检查你的图是否是二分图：

library(igraph)
film_data <- data.frame(
    
    "movie" = c("movie_1", "movie_1", "movie_1", "movie_2", "movie_2", "movie_2", "movie_3", "movie_3", "movie_3", "movie_4", "movie_4", "movie_4", "movie_4", "movie_5", "movie_5", "movie_5", "movie_6", "movie_6"),
    "actor" = c("actor_1", "actor_2", "actor_3", "actor_2", "actor_3", "actor_4", "actor_1", "actor_5", "actor_6", "actor_2", "actor_7", "actor_1", "actor_8", "actor_5", "actor_9", "actor_3", "actor_2", "actor_8")
)

#create directed graph 
graph <- graph.data.frame(film_data, directed=F)
graph <- simplify(graph)
plot(graph)

V(graph)$type <- V(graph)$name %in% film_data[,1]
is.bipartite(graph)
[1] TRUE

但是，您可以通过在两个参与者（actor_2 和 actor_3）之间添加链接来“故意破坏”该图，从而使该图不再是二分图：

film_data <- data.frame(
    
    "movie" = c("movie_1", "movie_1", "movie_1", "movie_2", "movie_2", "movie_2", "movie_3", "movie_3", "movie_3", "movie_4", "movie_4", "movie_4", "movie_4", "movie_5", "movie_5", "movie_5", "movie_6", "movie_6", "actor_2"),
    "actor" = c("actor_1", "actor_2", "actor_3", "actor_2", "actor_3", "actor_4", "actor_1", "actor_5", "actor_6", "actor_2", "actor_7", "actor_1", "actor_8", "actor_5", "actor_9", "actor_3", "actor_2", "actor_8", "actor_3")
)

#create directed graph 
graph <- graph.data.frame(film_data, directed=F)
graph <- simplify(graph)
plot(graph)

但是 R 仍然会说这个图是二分的：

V(graph)$type <- V(graph)$name %in% film_data[,1]
 is.bipartite(graph)
[1] TRUE

您可以通过在两部电影之间添加额外链接来进一步破坏此图表：

film_data <- data.frame(
    
    "movie" = c("movie_1", "movie_1", "movie_1", "movie_2", "movie_2", "movie_2", "movie_3", "movie_3", "movie_3", "movie_4", "movie_4", "movie_4", "movie_4", "movie_5", "movie_5", "movie_5", "movie_6", "movie_6", "actor_2", "movie_1"),
    "actor" = c("actor_1", "actor_2", "actor_3", "actor_2", "actor_3", "actor_4", "actor_1", "actor_5", "actor_6", "actor_2", "actor_7", "actor_1", "actor_8", "actor_5", "actor_9", "actor_3", "actor_2", "actor_8", "actor_3", "movie_2")
)

#create directed graph 
graph <- graph.data.frame(film_data, directed=F)
graph <- simplify(graph)
plot(graph)

但 R 仍将其称为二分：

V(graph)$type <- V(graph)$name %in% film_data[,1]
is.bipartite(graph)
[1] TRUE

有谁知道我做错了什么？最后两张图实际上是二分的吗？还是我错误地应用了代码？

澄清一下：所有无向图都是循环的吗？如果你有一个只有一种节点的无向图，它一定是二分的？

谢谢

【问题讨论】：

改用bipartite_mapping(graph)
哇，指挥棒！澄清一下， bipartite_mapping() 是否要求您首先确定每个顶点所属的类型？例如V(graph)$type
@MrFlick：所有无向图都是循环的吗？如果你有一个只有一种类型节点的无向图，它一定是二分的？
@Noob 如果图包含一个循环，则它是循环的。这与它是定向还是非定向无关。

标签： r graph data-visualization nodes

【解决方案1】：

确实，您创建的图不是二分图：“演员”部分有相邻的顶点。

函数is.bipartite()（或其名称）具有高度误导性。它只告诉您图形是否具有称为类型的所需顶点属性。它不检查构成图二分的其他特征。来源：?is.bipartite

【讨论】：