Public defence of my thesis on groups and reputation in social networks (2 september 2013, Louvain-la-Neuve).

1. 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

2. Overview
Social Networks
1 2
Community Detection Reputation & Negative Links

3. Overview
Social Networks
1 2
Community Detection Reputation & Negative Links

4. Social networks

5. Social networks

6. Social networks

7. Social networks

8. Social networks

9. Social networks

10. Social networks

11. Social networks

12. Social networks

13. Social networks

14. Social networks
I did not analyse these

15. Keep it simple

16. Keep it simple

17. Keep it simple

18. Keep it simple

19. Keep it simple
Node or Vertex

20. Keep it simple
Link or Edge

21. Keep it simple
Network or Graph

22. Overview
Social Networks
1 2
Community Detection Reputation & Negative Links

23. Overview
Social Networks
1 2
Community Detection Reputation & Negative Links

24. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster

25. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?

26. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?
Count links in community

27. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?
Count links in community
mc = 4

28. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?
Count links in community
mc = 4
Possible links?

29. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?
Count links in community
mc = 4
Possible links?
nc
2
= nc(nc1)
2 = 43
2 = 6

30. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?
Count links in community
mc = 4
Possible links?
nc
2
= nc(nc1)
2 = 43
2 = 6
4 links in community,
2 missing.

31. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Community or Cluster
But is it a good community?
Count links in community
mc = 4
Possible links?
nc
2
= nc(nc1)
2 = 43
2 = 6
4 links in community,
2 missing.
Want many links, few missing

32. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Bad community
Count links in community
mc = 5
Possible links?
nc
2
= nc(nc1)
2 = 54
2 = 10
5 links in community,
5 missing.

33. What is a community?
0
1
2
3
4
6 5
7
8
9
10
11
Are there better communities?

34. Make money
0
1
2
3
4
6 5
7
8
9
10
11
Get money for communities:
get 1 c for every edge in community,
pay c for missing edge in community.

35. Make money
0
1
2
3
4
6 5
7
8
9
10
11
Get money for communities:
get 1 c for every edge in community,
pay c for missing edge in community.
Suppose c = e0.50
4 edges, 2 missing:
4 0.5 2 0.5 = e1.00

36. Make money
0
1
2
3
4
6 5
7
8
9
10
11
Get money for communities:
get 1 c for every edge in community,
pay c for missing edge in community.
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

37. Make money
0
1
2
3
4
6 5
7
8
9
10
11
Get money for communities:
get 1 c for every edge in community,
pay c for missing edge in community.
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

38. Make money
0
1
2
3
4
6 5
7
8
9
10
11
Get money for communities:
get 1 c for every edge in community,
pay c for missing edge in community.
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

39. Better communities
Initial communities: e1.50
0
1
2
3
4
6 5
7
8
9
10
11

40. Better communities
Initial communities: e1.50
Move 0: get 2 0.5 = e1.00 extra
0
1
2
3
4
6 5
7
8
9
10
11

41. Better communities
Initial communities: e1.50
Move 0: get 2 0.5 = e1.00 extra
Move 5: get 3 0.5 = e1.50 extra
0
1
2
3
4
6 5
7
8
9
10
11

42. Better communities
Initial communities: e1.50
Move 0: get 2 0.5 = e1.00 extra
Move 5: get 3 0.5 = e1.50 extra
Move 11: get 1 0.5 = e0.50 extra
0
1
2
3
4
6 5
7
8
9
10
11

43. Better communities
Initial communities: e1.50
Move 0: get 2 0.5 = e1.00 extra
Move 5: get 3 0.5 = e1.50 extra
Move 11: get 1 0.5 = e0.50 extra
0
1
2
3
4
6 5
7
8
9
10
11
Final communities: e4.50

44. Better communities
Initial communities: e1.50
Move 0: get 2 0.5 = e1.00 extra
Move 5: get 3 0.5 = e1.50 extra
Move 11: get 1 0.5 = e0.50 extra
0
1
2
3
4
6 5
7
8
9
10
11
Louvain Algorithm

45. Real network
My own Facebook

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

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

48. Real network
My own Facebook c = e0.0025
526 internal links

49. Real network
My own Facebook c = e0.01
511 internal links

50. Real network
My own Facebook c = e0.10
491 internal links

51. Real network
My own Facebook c = e0.50
0 internal links

52. Resolution limit

53. Significance
Original partition (14 links)

54. Significance
Original partition (14 links)
Random graph (5 links)

55. Significance
Original partition (14 links)
Random graph (5 links) Find partition (11 links)

56. Overview
Social Networks
1 2
Community Detection Reputation Negative Links

57. Overview
Social Networks
1 2
Community Detection Reputation Negative Links

58. Social Balance
+
Leonard Sheldon

59. Social Balance
Leslie
+
+
Leonard Sheldon

60. Social Balance
Leslie
+
+
Leonard Sheldon

61. Social Balance
Leslie
+
Leonard Sheldon

62. Social Balance
Leslie
+
The enemy of my enemy is my friend
Leonard Sheldon

63. Social Balance
Leslie
+
The friend of my enemy is my enemy
Leonard Sheldon

64. Social Balance
Leslie
+
The friend of my enemy is my enemy
Leonard Sheldon
Socially balanced: + = +

65. Balanced Triads
Balanced Triads

66. Balanced Triads
Balanced Triads Unbalanced Triads

67. Balanced Triads
Balanced Triads
Two Factions

68. Changing Triads
Leslie
+
Leonard Sheldon

69. Changing Triads
Leslie
+
+
Leonard Sheldon

70. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon

71. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do

72. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +

73. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +

74. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +

75. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +
t

76. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +
t

77. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +
Compare friends with Leslie

78. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +
Compare friends with Leslie
Sheldon likes Leonard +

79. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +
Compare friends with Leslie
Sheldon likes Leonard +
Leslie dislikes Leonard

80. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
Ask Leonard what to do
Sheldon likes Leonard +
Leonard likes Leslie +
Effect ++ = +
Compare friends with Leslie
Sheldon likes Leonard +
Leslie dislikes Leonard
Effect + =

81. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
+
Leonard Sheldon
t
Compare friends with Leslie
Sheldon likes Leonard +
Leslie dislikes Leonard
Effect + =

82. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
Leonard Sheldon
t
Compare friends with Leslie
Sheldon likes Leonard +
Leslie dislikes Leonard
Effect + =

83. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
Leonard Sheldon
t
Compare friends with Leslie
Sheldon likes Leonard +
Leslie dislikes Leonard
Effect + =

84. Changing Triads
Sheldon’s relationship with Leslie changes Leslie
+
Leonard Sheldon
Ask Leonard what to do
Does not converge to
social balance
Compare friends with Leslie
Does converge to
social balance