class: center, middle, inverse, title-slide # An Introduction to Social Network Analysis (SNA) in R ## CORE Lab ### Department of Defense Analysis ### 2019-08-08 --- # Introduction * Purpose * Scope * SNA in R --- # What are social networks? * We emphasize the *social* in social networks. -- * Online and offline social networks .center[ ] --- # What is social network analysis? * SNA is a set of theories and techniques used to understand social structures. -- * We use SNA to identify strengths and vulnerabilities in social networks. --- # Social Network Example <small> * Person A is a member of Gang X and lives in Neighborhood 1. He has admittedly sold drugs to two individuals who reside in Neighborhood 1, Person D (male) and Person E (female). Person A is the brother of Person C and has two sisters, Actors F and G (both live in Neighborhood 2). Person A was arrested in the past with Person H (a close friend of B) and Person I. * Person B's affiliation is unknown and he lives in Neighborhood 3. Person B communicates with Persons F, G, and J. She is a friend of Person C, Person J (Gang X), and Person L. She lied to police about Person C's whereabouts on the night of a shooting last year. Person B hangs out with F, who knows L and N. * Person C is also a member of Gang X and lives in Neighborhood 2.Person H (Neighborhood 2), looks up to Person C. Person C's close friend, Person I (Neighborhood 2), is dating Person G and Person C communicates with Person J (Neighborhood 3). * Person D is a member of Gang Y and lives in Neighborhood 1.Person D regularly communicates with Person K ( member of Gang Z) and Person L. * Person E's affiliation is unknown. She is a close friend of Person K (Neighborhood 1) and is suspected of being a drug dealer. She dated Person K and Person A, and she hangs out with Person L (affiliation unknown) and Person M (affiliation unknown) from Neighborhood 1. --- # Social Network Example
--- # Social Network Example
--- # Social Network Example
--- # Social Network Example
--- # Common Misconceptions * Several misconceptions exist, but two appear to be the most prevalent. -- * SNA vs. Link Analysis * SNA vs. Social Media Analysis --- # Approach * Network Topography * Cohesive Subgroups * Centrality * Brokers and Bridges -- * Roles and Positions -- * Confirmatory SNA * Conditional Uniform Graph (CUG) Test * Quadratic Assignment Procedue (QAP) Test * Exponential Random Graph Models (ERGMs) * Stochastic Actor Oriented Models (SAOMs) --- # Centrality <small> |**Measure** | **Definition** | **Interpretation** | **Caveat** | |-----------|-------------------| -------------------------|-----------------------| |**Degree** (frequency)| Count of an actor's ties. | Actor activity; Direct power or influence, or ability to be influenced by others | In some cases, well-connected actors are the result of biased connections. | |**Eigenvector** (frequency) | Weights an actor's degree centrality by the degree centrality of its neighbors. | Indirect influence or power; Potential social capital. | In well-connected networks, it is often difficult to identify a single, or a few, potentially powerful actors. | |**Betweenness** (paths) | How often each actor lies on the shortest path between all pairs of actors. | Brokerage potential; Gatekeepers; Boundary Spanners | Betweenness assumes a desire for efficiency. Actors, resources, and information may not always follow shortest paths. | |**Closeness** (distance) | The average shortest path (i.e., geodesic) distance from an actor to every other actor in the network. | Actor levels of accessibility to others, and to material and non- material goods. | Not designed for use with disconnected networks. </small> --- # Hypothetical Network (Offline)
--- # Hypothetical Network (Offline)
--- # Attribute Table (Gang Network Top-5 Eigenvector) |**Rank** | **Name** | **Affiliation** | **Other Gang Connections** | **Crime Type** |---------|-------------| ----------------|--------------|------------| |1| O.G. (1)| County Boys | Almighty Angels,Blood Army, Guerrilla Posse, & 21st St. | Narcotic Offenses | |2| Fat Boy (.07) | Almighty Angels | County Boys | Burglary | |3| Freckles (.65)| Unknown | Almighty Angels & 21st St. | None | |4| Boots (.62) | Unknown | Almighty Angels |None | |5| 2 Tied at .56 | N/A | N/A | N/A | --- # Questions? <br> <br> <br> .center[ ] <br> <br> <br> <br> <br> <br> Dan Cunningham - dtcunnin@nps.edu