Information Technology Reference
In-Depth Information
-
Degree centrality
: The degree
d
of a vertex is the number of its incident edges.
For standardization, divide each score by
n
(
v
)
−
1,
n
is the number of nodes. In directed
graphs, edges have a direction associated. Accordingly, there are two different types
of degree centrality: in-degree, which is the number of edges pointing into a node
and out-degree centrality; i.e., the number of edges pointing out from a node.
Table 17.1
Out-Degree
Node Score Standard Score
1
3
3/8
2
2
1/8
3
2
1/8
4
2
2/8 = 1/4
5
2
1/8
6
2
1/8
7
2
1/8
8
2
1/8
9
2
1/8
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Closeness
: In contrast with centrality, closeness uses not only the maximum dis-
tance between the vertex of reference and all other vertices, but the sum of the
distances of this vertex and all other vertices.
In order to calculate the closeness centrality we need to calculate the inverted
score after we count the total number of steps to a node. For standardization, divide
ascoreby
(
n
−
1
)
and then take the inverse.
Table 17.2
Closeness
Node Score Standard Score
1
1/30
8/23
2
1/23
8/23
3
1/18
8/18
4
1/15
8/15
5
1/18
8/18
6
1/18
8/18
7
1/19
8/19
8
1/19
8/19
9
1/24
8/24
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Betweenness
: Betweenness is defined as the share of times that a node
i
needs
a node
k
(whose centrality is being measured) in order to reach a node
j
via the
shortest path. Putted bluntly, this measure basically counts the number of geodesic
