Public thesis defence: groups and reputation in social networks

Groups and Reputation in Social Networks
V.A. Traag
Promoteurs:
Paul Van Dooren, Yurii Nesterov
Jury:
François Glineur
Vincent Blondel
Marco Saerens
Patrick De Leenheer
ICTEAM
Université Catholique de Louvain
2 September 2013
Soutenance Publique

Overview
Social Networks
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Community Detection Reputation & Negative Links

Social networks
I did not analyse these

Keep it simple
Node or Vertex

Keep it simple
Network or Graph

What is a community?
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Community or Cluster

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But is it a good community?

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Count links in community

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mc = 4

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mc = 4
Possible links?

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mc = 4
Possible links?
nc
2

= nc(nc1)
2 = 43
2 = 6

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mc = 4
Possible links?
nc
2

= nc(nc1)
2 = 43
2 = 6
4 links in community,
2 missing.

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mc = 4
Possible links?
nc
2

= nc(nc1)
2 = 43
2 = 6
2 missing.
Want many links, few missing

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Bad community
mc = 5
Possible links?
nc
2

= nc(nc1)
2 = 54
2 = 10
5 missing.

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Are there better communities?

Make money
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Get money for communities:
get 1 c for every edge in community,
pay c for missing edge in community.

Make money
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Suppose c = e0.50
4 edges, 2 missing:
4 0.5 2 0.5 = e1.00

Make money
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Suppose c = e0.50
4 edges, 2 missing:
4 0.5 2 0.5 = e1.00
2 edges, 1 missing:
2 0.5 1 0.5 = e0.50

Make money
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Suppose c = e0.50
4 edges, 2 missing:
4 0.5 2 0.5 = e1.00
2 edges, 1 missing:
2 0.5 1 0.5 = e0.50
5 edges, 5 missing:
5 0.5 5 0.5 = e0.00

Make money
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Suppose c = e0.50
4 edges, 2 missing:
4 0.5 2 0.5 = e1.00
2 edges, 1 missing:
2 0.5 1 0.5 = e0.50
5 edges, 5 missing:
5 0.5 5 0.5 = e0.00
Total: e1.50

Better communities
Initial communities: e1.50
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Better communities
Move 0: get 2 0.5 = e1.00 extra
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Better communities
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Better communities
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Final communities: e4.50

Better communities
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Louvain Algorithm

Real network
My own Facebook c = e0.–
528 internal links

Real network
My own Facebook c = e0.0002
527 internal links

Real network
526 internal links

Real network
511 internal links

Real network
491 internal links

Real network
0 internal links

Significance
Original partition (14 links)

Significance
Random graph (5 links)

Significance
Random graph (5 links) Find partition (11 links)

Overview
Social Networks
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Community Detection Reputation Negative Links

Social Balance
+
Leonard Sheldon

Social Balance
Leslie
+
+
Leonard Sheldon

Social Balance
Leslie

+
Leonard Sheldon

Social Balance
Leslie

+
The enemy of my enemy is my friend
Leonard Sheldon

Social Balance
Leslie

+
The friend of my enemy is my enemy
Leonard Sheldon

Social Balance
Leslie

+
The friend of my enemy is my enemy
Leonard Sheldon
Socially balanced: +

Public thesis defence: groups and reputation in social networks

Public thesis defence: groups and reputation in social networks

Public thesis defence: groups and reputation in social networks

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Public thesis defence: groups and reputation in social networks