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Say I have this example graph, i want to find the edges connected to vertex 'a'
d <- data.frame(p1=c('a', 'a', 'a', 'b', 'b', 'b', 'c', 'c', 'd'), p2=c('b', 'c', 'd', 'c', 'd', 'e', 'd', 'e', 'e')) library(igraph) g <- graph.data.frame(d, directed=FALSE) print(g, e=TRUE, v=TRUE) I can easily find a vertex:
V(g)[V(g)$name == 'a' ] But i need to reference all the edges connected to the vertex 'a'.
393
The sum of the vertex degree values is twice the number of edges, because each of the edges has been counted from both ends. In your case 6 vertices of degree 4 mean there are (6×4)/2=12 edges.
The minus operator (' - ') can be used to remove vertices or edges from the graph. The operation performed is selected based on the type of the right hand side argument: If it is an igraph graph object, then the difference of the two graphs is calculated, see difference .
See the documentation on igraph iterators; in particular the from() and to() functions.
In your example, "a" is V(g)[0], so to find all edges connected to "a":
E(g) [ from(0) ] Result:
[0] b -- a [1] c -- a [2] d -- a If you do not know the index of the vertex, you can find it using match() before using the from() function.
idx <- match("a", V(g)$name) E(g) [ from(idx) ] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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