CODEWITHSUNDEEP
rigraphgraph-theory
EStark
EStark

Reputation: 193

Finding degree (centrality) of all nodes from an asymmetric (directed) adjacency matrix with R

network

I have an example of a simple network represented as an adjacency matrix.

I am trying to find the degree of each node/vertex (person)

As defined, the degree of a node is the number of connections it has to other nodes. By convention, in a directed (i.e. asymmetric) matrix, the sender of a tie is the row and the target of the tie is the column.

The adjacency matrix (with 1's on the diagonal): 

matrix(c(1,0,1,0,1,1,1,0,1,1,1,1,0,0,1,1), ncol = 4)

The result should be:

Bob: 2 Carol: 2 Ted: 3 Alice: 1

I tried to solve this writing a function, but it does not give a correct result (Carol = 1, not 2)

degree_centralty <- function(x) rowSums(x != 0)-1

Am I doing something wrong?

Upvotes: 1

Views: 483

Answers (1)

Julius Vainora
Julius Vainora

Reputation: 48211

By using rowSums or colSums you would count only one kind of connection. What you want is the union of the two and that can be found as follows:

degree_centralty <- function(x) rowSums(x + t(x) != 0) - 1
degree_centralty(A)
# [1] 2 2 3 1

where now x + t(x) is a symmetric matrix.

Upvotes: 1

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