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“Pajek”: Large Network Analysis

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Agenda

Introduction

Network Definitions

Network Data Files

Network Analysis

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Introduction to Slovenian Spider: Pajek

http://vlado.fmf.uni-lj.si/pub/networks/pajek/ Free software Windows 32 bit

Pajek 2.05

“Whom would you choose as a friend ?”

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Introduction

Its applications: Communication networks: links among pages or

servers on Internet, usage of phone calls Transportation networks Flow graphs of programs Bibliographies, citation networks

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Data Structures

Six data structures: Network(*.net) – main object (vertices and lines - arcs, edg

es) Partition(*.clu) – nominal property of vertices (gender); Vector(*.vec) – numerical property of vertices; permutation (*.per) – reordering of vertices; cluster (*.cls) – subset of vertices (e.g. a cluster from partiti

on); hierarchy (*.hie) – hierarchically ordered clusters and vertic

es.

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Introduction

Pajek 2.05

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Network Definitions

Graph Theory Graphs represent the structure of networks

Directed and undirected graphs Lists of vertices arcs and edges, where each arch

and edge has a value. To view the network data files: NotePad, EditPlus

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Network Data File

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Open Network Data File (*.net)

Number of Vertices

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Transform

Transform

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Report Information

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Visualization

Energy – Idea: the network is represented like a physical system, and we are searching for the state with minimal energy. Two algorithms are included:

Layout/Energy/Kamada-Kawai – slower Layout/Energy/Fruchterman-Reingold – faster, drawing in a plane or space (2D or

3D), and selecting the repulsion factor

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Network Creation

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Partitions

File name: *.clu

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Degree