Introduction to Complex Systems and Social Network Analysis

Arif KhanComplex Systems Research Centre

The University of Sydney

Lecturer (on leave)Department of CSE, BRAC University

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

What is Social Networks

• Relationship between Social Entities

A B

CD

Nodes are Entities/ActorsCan be people, organization, countries

Edges are relationshipCan be Friendship, Transaction, Trust, Relationship

Some Social Network

• Migratory Bird Network

Some Social Networks• Relationship network in a U.S. high school. Girls are pink, boys

are blue

Some Social Network

• Ingredients Network

Why Social Network Analysis?

• Because our choice/behavior has social context, we are influenced by others

Some Research Facts

• Relationships are mostly mutual. If you like me, I will like you.

A B

• Friend of my friend will eventually be my Friend

A B

C

Some Research Facts

• Making and Maintaining friendship is costly.• Average person can maintain only 150

intimate relationship.• So this friendship network is hardly possible.

Some Research Facts

• This is a small world. On average each person of world has a friendship distance of 6

• There are on average 3.74 people in between any two facebook users.

Complex System

• Social Networks are one type of Complex System, they have all the properties discussed above.

• Complex Systems– Have large number of actors/nodes– Changes over time– They are resilient.

Centrality: finding important Nodes

• Degree Centrality

A B

C

D

E

I am So popular!!

A B

C

D

E

I am social,

I love

everyone!!

B has high in-Degree

B has high out-Degree

Centrality: finding important Nodes

• Betweenness Centrality‘A’ has high Betweenness centralityIt can control Information, can control business,Can manipulate information

Centrality: finding important Nodes

• Closeness centralityI may not have

lots of friend. But I have powerful

friend, enough for me

High (not highest) closeness centrality

Example of SNA software (Gephi)

• Analyze my Facebook network• <OPEN GEPHI outside>

Social Network Analysis as CSE perspective

• Developing efficient algorithms (graph algorithm, approximation algorithm)

• Developing efficient graph/mathematical models of real world Social Networks

• Developing data mining software, centrality measures

• And many more…

If you are interested…

• This is relative new research area.• Almost all universities have research centers

related to Social Network analysis, complex system, data mining etc.

• Complete the online course (FREE!) from www.coursera.org/course/sna

THANK YOU

Questions?

Important Links: www.coursera.org/course/snaMy Mail: arif.khan@sydney.edu.au

Pictures taken from various sources, may be copyrighted. Used for Educational purpose only