Network graphs are used to rapresent data based on the concept of “linked” items: data are intrinsically structured with relationships of connection.
In network graphs, data items are represented with nodes, connections are represented with edges.
Graph edges can be directed or undirected. The degree of a node is the number of links connected to it (In-degree and out-degree for directed graphs). Graph edges can have values (weights) on them. These values can be nominal, ordinal or quantitative.