From the Synthetic networks slide deck (didn’t have a chance to go over them at that time) By: Ralucca Gera, NPS.

Slides:

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Presentation transcript:

From the Synthetic networks slide deck (didn’t have a chance to go over them at that time) By: Ralucca Gera, NPS

Generating Barabasi-Albert

Generating Barabasi-Albert

Generating Barabasi-Albert networks http://networkx.lanl.gov/reference/generated/networkx.generators.random_graphs.barabasi_albert_graph.html#networkx.generators.random_graphs.barabasi_albert_graph

Many modifications of this model exists, based on: Modified BA Many modifications of this model exists, based on: Nodes “retiring” and losing their status Nodes disappearing (such as website going down) Links appearing or disappearing between the existing nodes (called internal links) Fitness of nodes (modeling newcomers like Google) Most researchers still use the standard BA model when studying new phenomena and metrics. Why? It is a simple model, and it was the first model that brought in growth (as well as preferential attachment)

Section 1: Graph theory: Section 2: Complex networks: Overview Section 1: Graph theory: Origins (Eulerian graphs) Section 2: Complex networks: Random graphs (Erdos-Renyi) Small world graphs (Watts-Strogatz) Scale free graphs (Barabasi-Albert) The configuration model (Molloy-Reed) The random geometric model

The Malloy Reed Configuration model

The configuration model A random graph model created based on Degree sequence of choice (can be scale free) Maybe more than degree sequence is needed to be controlled in order to create realistic models

Section 1: Graph theory: Section 2: Complex networks: Overview Section 1: Graph theory: Origins (Eulerian graphs) Section 2: Complex networks: Random graphs (Erdos-Renyi) Small world graphs (Watts-Strogatz) Scale free graphs (Barabasi-Albert) The configuration model (Molloy-Reed) The random geometric model

The Random Geometric model

Random Geometric Model Again the connections are created at random, but based on proximity rather than preferential attachment (such as ad hoc networks) Recall that BA was introduced based on the data obtained from the Web, where physical proximity is irrelevant. But if one would want to model something like the Internet, then proximity is relevant There is no perfect model for the world around us, not even for specific types of networks No model has been introduced for the Internet

An example of a random geometric https://www.youtube.com/watch?v=NUisb1-INIE

A zoo of complex networks

Random, Small-World, Scale-Free Scale Free networks: High degree heterogeneity Various levels of modularity Various levels of randomness Man made, “large world”: http://noduslabs.com/radar/types-networks-random-small-world-scale-free/

Networks and their degree distributions We tend to characterize networks by their degree distributions: Random graphs iff Poisson degree distribution Scale free iff power-law degree distribution. But they are not! Rather: If G is a random graphs, then G has Poisson degree distribution If G is scale free, then G most probably has a power-law degree distribution. If G was constructed using preferential attachment, then G has a power-law degree distribution.

Python References to the classes that exist in python: http://networkx.lanl.gov/reference/generators.html