CODEWITHSUNDEEP
rigraph
user3631619
user3631619

Reputation:

Creating a igraph object with graph.adjacency doesn't preserve the degree of each node?

I have a network in the form of an adjacency matrix, and I am trying to create a plot that shows the degree distribution of the network.

First of all, I used the function "graph.adjacency" to create an igraph object from the adjacency matrix, and I obtained the connectivity for each node with the "degree" function:

graphobj<-graph.adjacency(adjacencymatrix, mode="undirected")

degreenetwork<-degree(graphobj)

Then I have calculated the degree of each node with an other method:

degreenetwork2<-apply(adjacencymatrix, 1,sum)

and I have noticed that the degree of the nodes is not always preserved. In fact the the two methods give me different value of connectivity for the nodes. For example:

mean(degreenetwork)

[1] 156.068

mean(degreenetwork2)

[1] 78.034

min(degreenetwork)

[1] 17

min(degreenetwork2)

[1] 0

max(degreenetwork)

[1] 521

max(degreenetwork2)

[1] 452

Is there something wrong, or am I not using correctly the igraph package?

Regards

Gianni

Upvotes: 0

Views: 813

Answers (1)

Gabor Csardi
Gabor Csardi

Reputation: 10825

You are possibly double counting edges, because your matrix is probably symmetric. Or maybe your matrix is not binary. It is hard to tell for sure, because you did not provide a reproducible example, so we have no idea what is in your matrix.

See How to make a great R reproducible example?.

Upvotes: 0

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