1. Màster en Direcció d'Empreses / Master in Management
SNA: An Introduction
José Luis Molina
Màster en Direcció d'Empreses / Master in Management

2. What do we mean by “social networks”?
Social Media (twitter, Facebook, Whatsapp…)
Market oriented: Social Networking Sites
Adopted by Mass-Media.
Convergenge of social and tecnological networks (Kleinberg 2008) …
A metaphor about complexity
Castells, The Network Society(1999).
(…)
Emergent social structures
Communities, social circles, quasi-groups (Boissevain 1968) …
Transnational fields – diffusion of ideas, habits …
Informal organizational chart.
Industrial districts!

3. A long history ...

4. Theoretical questions …
Identification of the effect of emerging social structures in individual or collective behavior (rumors, Epstein 1969; strike, Kapferer 1972; political mobilization, Srinivas & Béteille ).
Divergence between cognitive data and behavioral data.
Relations between micro and macro social structures. Contagion - Influence, strong / weak ties. RDS ...
Intracultural variation of local ecological knowledge.
Synchronicity of human activity (cities, regions, world).
Other ... (Adler-Lomnitz, Dunbar ...).

5. Basic definitions: centrality, cohesion, positions and structures

6. Whole networks– egonetworks, egocentric networks /personal networks
A whole/complete network is a collection of nodes and ties taken from a specific field of interaction (a classroom, a organization, an internet community…).

7. Boundary specification (Laumann et al. 1983)
Nominalistic
Imposed by the researcher’s analytical interests (“the network of interlocking directorates in Spain”).
Realistc
Boundaries reported by the participants (“people in this neighboorhod”).
Representative sampling is not possible (or by sampling 80%).
Important/influential people can be easily identifed (indegree / nominations).

8. Ego-centric analysis: ego networks
A “egonetwork” is the neigborhood of a given ego within a whole network.
Every ego is a node of the whole network.
The analysis focuses on the egonetwork level, including ego.

9. Ego-centric networks /personal networks
A“personal network” is the set of people and ties of a given individual in different fields of interaction, along with the alter-alter ties.
Ego is typically not represented.
The analysis is conducted at the individual level.
Representative sampling is applicable.

10. Combination…
Personal networks can be combined into a whole network.

11. Network data...
Name generators (cognitive data): questions that provide names of people in return.
Each name generator can generate a different network.
Digital activity logs (time, location, from, to, content … behavioral data) .
Usually many observations and few ítems by each case (phone calls, Facebook likes, etc.)
Others (letters, official registers, etc.)

12. Types of name generators…
One name generator vs. multiple name generator
Free list vs. fixed list.
Free size / fixed number of nominations.

13. Network ties can be… Bynary (1, 0) or valued (e.g. 0-5).
Oriented or reciprocal

14. “Name interpreters” / attributes
The list of descriptives of each alter nominated:
Sociodemographics
Ego-alter closeness.
Geographic location. …

15. Types of matrices
One-mode= same set of actors/nodes/vertices on rows and columns.
Two-mode= one set of actors on rows and a different set of actors or events on columns. Also called Affiliation Matrices.
It is possible to convert two-mode matrices to one-mode (rows * rows or columns * columns).

16. ... Matrix one-mode...
AMRVGBEGJSJMMOCRPPGGJLMAFGDE
1 AMG
2 RVT
3 GBB
4 EG
5 JSP
6 JMF
7 MOS
8 CR
9 PP
10 GG
11 JLM
12 MAR
13 FG
14 DES

17. … and its sociogram ...

18. Some basic concepts from graph theory …
Path
Geodesic
Component
Diameter …

19. Node level: centrality measures

20. Network level: density or av. degree, component, centre-perifery

21. Group-level Group detection following the cohesion strategy.
Newman-Girvan
Tab “Analysis”: grouping, clustering, modulartiu, girvan-Newman  apply
This operation creates a new attribute that can be seen in the Attribute Manager and gives a value to each group. This value can be used to differentiate / color / merge the different groups.

22. Collection of network data…
Link List …
Ego, alter, value:
Tom Cruise, Nikole Kidman, 5
Tom Cruise, Penélope Cruz, 3
Nikole Kidman, Tom Cruise, 2
Nikole Kidman, Penélope Cruz, -5 o
Nikole Kidman, Penélope Cruz, 0
(in case of absence, the dyad means a value of “1”).
Attributes …
Artist, sex, age, nationality, or degree of innovation, market share…

23. Import Link List + Atributes to visone
visone.info
Webstart or download
Ejecutar el programa
Descargar fichero CSV con
los enlaces (en el escritorio).
los atributos (en el escritorio)
Importar (file > open) en
primer lugar el fichero links.

24. Attribute manager

25. Análisis a nivel de red
Medidas de cohesión (densidad, reciprocidad, transitividad …).
Componentes
Estructura centro-periferia
(…)
Tab Analysis: task: indexing; class: network; index: network statistics, seleccionar densidad, average degree, conn. components, # nodes in max core.
Apply
Attribute Manager> Show/edit.

27. Some links... INSNA http://www.insna.org/ Web Redes
Revista REDES