MARK3054 Lecture 11: MARK3054 Topic 11
Topic 11: Network Analysis and Social Network
Why do networks matter? To find people who are connected (also tend to be more alike)
What is network analysis?
A method by which one can analyse the connections across individuals/groups/institutions.
Focuses on interaction rather than on individual behaviour (allows us to examine how the
configuration of networks influences how individuals/groups/organisations behave).
The unit of interest in a network are the combined sets of actors and their relations.
Actors (points) aka nodes, vertices, points
Relations (lines) aka edges, links, arcs, lines or ties
A relation can be:
1. Binary or valued
a. Binary is whether there is a connection or not
b. Valued includes the strength of the connection with a number, or via line thickness
2. Directed or undirected
a. Directed is a one way network, and you must show each direction
b. Undirected is a two way directed network
To choose the most important node, note who has the most connections and then try and convince
them to spread the word.
How to transform pictorial network structures into matrices:
• So computers can understand
• E.g. for a network with 5 nodes, make a 5x5 matrix
• Whenever there is a link, put a 1.
• Check directions! If 2-way put it in a*b and b*a but if only one direction put on only one,
with the direction going sender to receiver (RIGHT TO LEFT) And in the matrix read vertical
then horizontal
• However, when there are too many, the matrices can get too huge. Instead, use adjacency
or arc lists
Importance of a node:
• Degree centrality (number of links that a node has)
o Count the number of links a node has
• Closeness centrality (index based on the average length of the shortest path between a node
and all other nodes) (every node has a closeness centrality)!
o Write down how many links it takes to go from the target node to all other nodes
o Average out that number, and that is the closeness centrality
• Betweenness centrality (index based on the number of times a node acts as a bridge along
the shortest path between 2 other notes) aka which nodes have the most impact on the
spread of information through the network?
o List out all pairs except the node you are trying to find the betweenness centrality
for
o Then, write whether or not the shortest path includes the target node (1 point if the
target node is in the shortest path, 0.5 points if it ties with another path)
o Add up all the Y and express as a fraction/all
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