[igraph] Graph.density => Usage in directed and undirected networks

[Carlos Eduardo]

Hello,

 

As it is showed bellow, I have two networks being one “directed” and other “undirected”. The relations are the same in both network, besides the fact that in directed network I have two edges linking each pair of vertex. I read in books like Wasserman & Faust (1994) that in directed networks it is necessary to divide the density by 2. I understood this argument in the “book”, but when I used the command “graph.density(g)”, the output was the same to both networks. So, it seems that isn’t necessary to divide the igraph output by 2. Is there any technical explanation to how igraph deals with this matter?

 

Thanks in advance,

Cadu

 

Network 1

Vertices: 4

Edges: 4

Directed: FALSE

Edges:

[0] '1' -- '3'

[1] '2' -- '3'

[2] '3' -- '4'

[3] '1' -- '2'

 

Network 2

Vertices: 4

Edges: 8

Directed: TRUE

Edges:

[0] '1' -> '3'

[1] '3' -> '2'

[2] '3' -> '4'

[3] '1' -> '2'

[4] '3' -> '1'

[5] '2' -> '1'

[6] '2' -> '3'

[7] '4' -> '3'