如何获得iGraph对象直径的所有最短路径？

Question

I want to get all the longest shortest paths for iGraph object. There is this function

get.diameter (graph, directed = TRUE, unconnected = TRUE) 

But it returns only one path. So if there are many shortest paths of the length of the diameter, then it returns the first one found

Answer 1

You can easily extract which nodes are connected at what lengths using the shortest-distance matrix returned by shortest.paths(graph). In R, you can use which() and arr.ind=TRUE like so:

longest.shortest.paths <- function(graph){
    # Return edgelist of all node-pairs between which the shortest path
    # in a graph are the longest shortest path observed in that graph.

    # Get all the shortest paths of a graph
    shortest.paths = shortest.paths(graph)

    # Make sure that there are no Inf-values caused by isolates in the graph
    shortest.paths[shortest.paths == Inf] <- 0

    # What nodes in the distance matrix are linked by longest shortest paths?
    el <- which(shortest.paths==max(shortest.paths), arr.ind=TRUE)
    colnames(el) <- c("i","j")
    (el)
}

graph <- erdos.renyi.game(100, 140, "gnm", directed=FALSE)
longest.shortest.paths(graph)