Subset igraph graph by label

Question

I am trying to subset a igraph graph by an edge characteristics (like its label). In the reproducible example I have shamelessly stolen from another post with a little modif

Answer 1

how about:

gfam <- subgraph.edges(graph=g, eids=which(E(g)$label=="FAM"), delete.vertices = TRUE)
gbf <- subgraph.edges(graph=g, eids=which(E(g)$label=="BF"), delete.vertices = TRUE)

Suggestion for igraph/network analysis tutorial/shameless plug: http://sna.stanford.edu/rlabs.php

Answer 2

I suggest you read ?V and ?E to see how to select edges and vertices. A quite compact and readable solution to your question is

subgraph.edges(g, E(g)[label=="FAM"])
subgraph.edges(g, E(g)[label=="BF"])

This removes the vertices as well, if they don't have an incident edge of the specified label. See ?subgraph.edges for details.