Networks are “groupy”
- Network formation processes lead to “groupy” networks
- Foci (Scott Feld)
- Triadic closure
- Homophily
We may want to identify groups
- Understanding where information is likely to flow / be held in common
- Social media marketers identifying “interest groups”
- Researchers understanding a scientific field
- Understanding relationships between groups
Early approaches to identify groups
- Components
- Everyone connected in any way
- Usually not useful - (nearly) everyone is connected
- Cliques
- Everyone is connected to everyone else in group
- Expanded to n-cliques (everyone in group is at a distance of n or less from everyone else)
- Long, stringy groupings
Early approaches (continued)
- K-plexes
- All members of group are connected to all but k other members
Many groups have a core and a periphery
- New people start on the periphery (Legitimate Peripheral Participation)
- People leaving move to the periphery
- Different levels of dedication / resources
- Evolutionary perspective
- In order for groups to survive, there has to be a core
Implications
- Those in core more likely to have knowledge, experience, and to stick around
- Identify the most dedicated group
- Identify those in danger of leaving / needing help
Ways of measuring
Ways of measuring
- K-cores
- Every node gets a value: the largest k where they are in a subgraph where everyone else has degree of at least k
- Rich-club coefficient
- How much are those with high degree connected to each other