Graph Theory

Graph theory concerns graphical models of pairwise relations between objects (e.g. Hansen, Shneiderman, Smith, 2011). Such a graph consists of nodes (or vertices), representing the objects, and edges (or lines), representing the relationships between them (West, 2000). Graphs are often represented by drawing a dot or circle for every node or vertex, and drawing an arc between two vertices if they are connected by an edge (ibid). Graphs can be directed or undirected. In directed graphs arrows are used (ibid).

These graphs can be used to represent connections between websites, decisions, but also between actors in social networks (see social network, SNA). There are many good introduction books (for example West, 2000) and applications for social media (for exampple Hansen et al., 2011)

References:

Hanneman, R. A., & Riddle, M. (2005). Introduction to Social Network Methods. from http://faculty.ucr.edu/~hanneman/nettext/Introduction_to_Social_Network_Methods.pdf

Hansen, D. L., Shneiderman, B., & Smith, M. A. (2011). Analyzing social media network swith NodeXL. Insigths from a connected world. Amsterdam: Elsevier.

West, D.B. (2000). Introduction to Graph Theory. Pearson (2nd edition).