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我有一个图形对象，g并想在1.5中创建g_sub一组顶点的邻域的子图。v_matchesgorder

换句话说，当且仅当这些顶点也连接到顶点时，我想找到哪些顶点连接到v_matches（顺序 1），哪些顶点连接到 order==1顶点。v_matches

在非技术术语中，我想找到“朋友的朋友（订单 2），前提是这些朋友也是我的朋友（订单 1.5）”。我找不到在igraph.

我编写的代码计算 2 的邻域v_matches，但我希望它计算 1.5 的顺序。很感谢任何形式的帮助。

v_matches <- which(V(g)$SomeVertexAttribute==SomeValue)

g_sub <- induced.subgraph(graph=g,vids=unlist(neighborhood(g,order=2,nodes=v_matches)))

更新：这是我编写的一个函数和一些代码，用于将order=2子图转换为order 1.5. 但是，我不相信它工作正常。

Order2ToOrder1.5 <- function(g_sub,categoryValue) {
  # get the new indexes of the 'ego' sites for the subgraph
  matches_subgraph_gsub <- which(V(g_sub)$`Categorical 1`==categoryValue)
  # get the edge list of the subgraph
  edgelistTemp <- get.edgelist(g_sub)
  # get unique "from" values
  uniqueFrom <- unique(edgelistTemp[,1])

  badVerts <- c() # yes, I know it is bad form to append to a vector using a for loop...
  for (i in 1:length(uniqueFrom)){
    # we find the immediate neighbours of each vertice
    tempGraph <- as.vector(neighborhood(graph=g_sub,order=1,nodes=uniqueFrom[i])[[1]])
    # if the neighbourhood does not contain one of the 'ego' sites (i.e. in matches_subgraph_gsub), then we flag this vertex for deletion
    matchTemp <- match(tempGraph,matches_subgraph_gsub)
    if (length(which(is.na(matchTemp)))==length(matchTemp)) {badVerts <- append(badVerts,uniqueFrom[i])}
  }

  # now we can delete these from the subgraph:
  g_return <- delete.vertices(g_sub,badVerts)
}

categoryValue <- 21
matches <- which(V(g)$`Categorical 1`==categoryValue)
g_sub <- induced.subgraph(graph=g,vids=unlist(neighborhood(graph=g,order=2,nodes=matches)))

# We can use the new function to convert from order2 to order1.5:
g_sub_1.5 <- Order2ToOrder1.5(g_sub,categoryValue)
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