Networks and the Digital HumanitiesTHATCamp PittsburghOctober 5th and 6th, 2013Dr. Elaine Frantz ParsonsAssociate Professor of HistoryDuquesne University&Dr. Thomas LombardiAssistant Professor Computing & Information StudiesWashington & Jefferson College

Vertices

Edges

From Graph Theory to Networks

People

Friendship

Alice

Bob

Chuck

Constructing Networks: Method

Christ

Mary

John

Giotto, Crucifixion, Tempera on wood, ca. 1290-1300. Source: commons.wikimedia.org

Network of Saints in Images of St. Francis

Analyzing Network ModelsCentrality

DegreeBetweenness

Weighted EdgesDirected EdgesClusteringAffiliation NetworksCommunity Detection

Degree CentralityNumber of links connected to a node

Node A has a degree centrality of 6

Nodes B, C, D, E, F, G: degree of 1

Degree centrality measures the ease with which information can reach a particular node

Betweenness Centrality% of shortest paths running through a node

H has a low degree, but high betweenness

Cut vertices

Bridges

Betweenness confers the ability to control the flow of information in a network

Network of Characters in Hamlet

Franco Moretti. Network Theory, Plot Analysis. New Left Review. 2011.

Edge WeightsSome links between nodes are more important than others

Edges can be weighted to record the importance of a connection

For example, some characters interact more than others in a novel

Each interaction increases the weight of the link between characters

The Rhyme Scheme of The Raven

Edge Direction

Letter 44:The Vicomte de Valmont to the Marquise de Merteuil

Vicomte de

Valmont

Marquise de

Merteuil

Dangerous Liaisons: Network of Letters

ClusteringSome nodes are situated in extremely dense parts of the network

Node E is entirely embedded: all of the node’s neighbors are neighbors

Other nodes are in relatively sparse parts of the network

None of I’s neighbors are neighbors

Network of Relationships in FlorencePadgett & Ansell, 1993

Network structure accounts for Medici rise to power in the 1430s

Brokerage

Constraints amongst old families of Florence made them ineffective

Clustering

Affiliation NetworksNetworks often track more than 1 kind of entity

Students and their classes

These networks are flexible because they can be transformed into a network of students and a network of classes

Networks can also have more than one type of link: multi-relational networks

Union County Affiliation Network

Community DetectionIn large networks, we frequently want to find the dense clusters of nodes

These often represent communities of interest

These communities often relate to other groups in interesting ways

Communities within William Faucett’s K-Neighbors

Hands-on Activities

Flash drives contain some of the networks we’ve discussed

Perform some basic analysis of a network with Pajek

Create your own network model for analysis in Pajek

Experiment with networks