CODEWITHSUNDEEP
rgraph
Nicolas Rosewick
Nicolas Rosewick

Reputation: 1998

R: Extract connected graphs

I've a undirected graph composed of ~300 nodes. The graph is composed of multiple connected graphs (example below with a undirected graph composed of 5 connected graph). Using R, how can I extract each connected sub-graph, and their node and edge count. My graph is represented by a two-column data.frame:

node1 node2
node1 node3
node2 node5
...

With the example below, the expected result would be

Subgraph NodeCount EdgeCount
1        2         1
2        4         3
3        2         1
4        2         1
5        2         1

Thanks

enter image description here

Upvotes: 0

Views: 346

Answers (1)

lukeA
lukeA

Reputation: 54247

You can do it like this:

library(igraph)
set.seed(1)
g <- simplify(graph.compose(graph.ring(10), graph.star(5, mode = "undirected"))) + edge("7", "8")
dg <- decompose.graph(g)
t(sapply(seq_along(dg), function(x) c(Subgraph = x, NodeCount = vcount(dg[[x]]), EdgeCount = ecount(dg[[x]]))))
#      Subgraph NodeCount EdgeCount
# [1,]        1         7        12
# [2,]        2         2         1
# [3,]        3         1         0

The example graph looks like this (plot(g)):

enter image description here

Upvotes: 3

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