What is it?
- You have different regions within the network that interact more heavily within their regions than they do across the network
- Classifications / Reasons for Community Structures
- Mutuality of ties aka cliques
- Not robust – one missing link can disqualify a clique
- Not interesting – everybody is connected, no core-periphery and no centrality measures apply
- The maximal distance between any two nodes is a subgroup is designated by n
- The diameter (the longest path between any two nodes) may be greater than n
- You can leave nodes out
- You need to know at least a proportion (p) of the clique
- Each node within a group is connected to k other nodes in the group
- This can be too stringent because you can end up leaving out certain nodes
- Frequency of ties among members
- Closeness or reachability of subgroup members
- Relative frequency of ties among subgroup members compared to nonmembers (proportion)
- Bipartite networks
Why look for community structure?
- It gives you a clear depiction of a network (company structure, school structures, government structures)
- It can help you predict future occurrences
- Regions (groups of nodes) after affected by their region and will not be influenced by non-region specific changes.
- Ways to partition communities
- Some similarity between two nodes is calculated and begin to nest them
- There’s no way to know 100% that the communities you’ve found are the most optimal
- For each node you define a community (“in the same community?” - yes or no is answered per node)
- Clique Percolation
- Similar to modularity but not as stringent – it allows for nodes to share communities.
Above are notes I’ve taken to keep track of the material covered in the Social Network Analysis course I am taking on Coursera. Notes are derived from week-based video lectures and supplemental information I’ve found online to help clarify certain concepts. If you are taking this course, most of the information below will be found in Week 4 associated material. If you are not taking the course, I hope you find the information below helpful in your search