R：如何从根节点遍历到iGraph数据对象中的每个叶节点并获取路径？

Question

我是R的新手，我有一个图形对象，它是从数据框对象“ allTog”创建的，如下所示：

library(igraph)
df.g <- graph.data.frame(d = allTog, directed = TRUE)
plot(df.g, vertex.label = V(df.g)$name)

allTog数据帧由下式给出

allTog <- data.frame(
    source = c("chamber", "chamber", "chamber", "chamber", "chamber", 
    "check", "check", "issue", "issue", "issue"), 
    target = c("check", "issue", "leak", "process", "found", "power", 
    "customer", "customer", "wafer", "replaced") 
    )

列“ row.names”和“ values”在这里没有意义。

如何从每个根节点（在本例中为“ chamber”）遍历到每个叶节点并获取路径，即所有节点（顶点）名称？我正在寻找一个通用的解决方案，因为我的根节点可以随代码的每次运行而变化。例如，在下一次运行中，根节点可以是“ issue”。

我想要的输出是：

chamber->check->power
chamber->issue->replaced
chamber->process
chamber->issue->customer

等等...

Answer 1

怎么样

root <- "chamber"
leafnodes <- sapply(V(df.g), function(x) length(neighbors(df.g,x))==0 )
paths <- get.all.shortest.paths(df.g, V(df.g)[root], leafnodes)$res
sapply(paths, function(vs) paste(V(df.g)[vs]$name, collapse="->"))

这列出了您可以访问的所有叶节点

# [1] "chamber->leak"            "chamber->process"         "chamber->found"          
# [4] "chamber->check->power"    "chamber->issue->customer" "chamber->check->customer"
# [7] "chamber->issue->wafer"    "chamber->issue->replaced"