我有一个包含多个不连通组件的igraph。例如:
library(igraph)
g <- simplify(
graph.compose(
graph.ring(10),
graph.star(5, mode = "undirected")
)
) + edge("7", "8")
在这个例子中,节点9是它自己的图形,节点7和8也是,其余的节点形成第三个图形。
我想将它们分开处理,所以我想将单个igraph转换为3个igraph列表(按连接性拆分)。
我编写了一些代码来实现这一点,但效率很低且相当糟糕。
split_graph_into_connected_subgraphs <- function(g)
{
adjacency_list <- get.adjlist(g)
connected_nodes <- lapply(
adjacency_list,
function(adjacent_nodes)
{
new_nodes <- out <- adjacent_nodes
# Keep finding nodes that are adjacent to ones we already know about,
# until we find no more
repeat
{
doubly_adjacent_nodes <- Reduce(union, adjacency_list[new_nodes])
new_nodes <- setdiff(doubly_adjacent_nodes, out)
if(length(new_nodes) == 0)
{
break
}
out <- union(out, new_nodes)
}
sort(out)
}
)
# Single value nodes should contain themselves, not be empty
connected_nodes <- ifelse(
vapply(adjacency_list, length, integer(1)) == 0,
seq_along(connected_nodes),
connected_nodes
)
# We don't care about repeats, just the unique graphs
connected_nodes <- unique(connected_nodes)
# Get the subgraph from each
lapply(
connected_nodes,
function(nodes) induced.subgraph(g, nodes)
)
}
list_of_subgraphs <- split_graph_into_connected_subgraphs(g)
lapply(list_of_subgraphs, plot)
有没有更简洁的方法来拆分图形?