Understanding and Interpreting Your Network

John R. Ladd | jrladd.com/slides/networkbasics

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Basic Parts

Networks are made up of…

  • Entities (entity = node/vertex/actor)
  • Relationships (relationship = edge/link/tie)
  • We’ll use “nodes” and “edges”

Nodes and Edges have Attributes

Node Attributes

  • numerical (size)
  • categorical (color)

Edge Attributes

Directed and Undirected Edges

Weighted and Unweighted Edges

Edge Types

Multiple Edges “in a row” Make a Path

Path & Diameter

(& Average Shortest Path Length)

Some special kinds of nodes

Isolates

Hubs

Bridges

Measuring a node’s “importance” with centrality

Degree

Strength

Betweenness

Different kinds of entities or nodes

Unipartite/unimodal

Bipartite/bimodal

Bipartite (cont.)

Multipartite/k-partite/multimodal

Groups of nodes within a network

Connected components

Cliques and clustering

Clustering Coefficient

Image from Wikipedia

Communities and community detection

Density

A Sparse Network

A Dense Network

There are many ways to visualize a network

Adjacency Matrix

Tilman Piesk, via Wikipedia

Adjacency List

  • A adjacent to B,C
  • B adjacent to A,C
  • C adjacent to A,B

Other Important Concepts

Triadic Closure

Assortative mixing/Homophily

Preferential Attachment

Weak Ties

Small World Network

  • low average path length
  • low clustering coefficients
  • degree distribution follows power law (a few large hubs)
  • low diameter (usually around “six degrees”)