Introduction to network and graph visualization

A network or graph in its simplest definition, includes nodes and edges.

Nodes: could be visualized as vertices in 2D space.

Edges: could be visualized as connectivity of nodes in 2D space that would be shown as a line or curve between nodes that connect them together.

In this example, nodes are shown as dots where the Label shows the first name of people and Attribute shows their gender (1: Male, 2: Female). Edges are defined between source and target ids to show their friendship.

Besides custom defined Attributes, one intrinsic property of graph or network is the degree of nodes or number of connections of the nodes in a graph or network. This degree of connection could be visualized by attributing colors to the nodes:

Downloading and installing gephi software:

• Download the Gephi software version 0.9.2: gephi.org
• After downloading and installing the Gephi software, open it, and go to Tools ----> Plugins
• Click on Available Plugins and download GeoLayout and Multimode Networks Transformation plugins.

Downloading data:

• Download the US COVID-19 dataset at the county level for April 20, 2020 (from New York Times): https://bit.ly/3cdnyKJ
• Download the South Carolina COVID-19 dataset at the county level for April 20, 2020 (from New York Times): https://bit.ly/2zdUy7U
• Download Mapping Letter Over Europe (from Martin Grandjean Website):
• Nodes: http://www.martingrandjean.ch/wp-content/uploads/2015/10/Nodes1.csv
• Edges: http://www.martingrandjean.ch/wp-content/uploads/2015/10/Edges1.csv