Investigating islands and continents – connected components

If you take a look at the subgraph visualization, you may notice that there is one large cluster of nodes, a few small islands of nodes (two or more edges), and several isolates (nodes with no edges). This is common in many networks. Very often, there is one giant supercluster, several medium-sized islands, and so many isolates.

This presents challenges. When some people are new to network analysis, they will often visualize the network and use PageRank to identify important nodes. That is not nearly enough, for anything. There are so many different ways to cut the noise from networks so that you can extract insights, and I will show you several throughout the course of this book.

But one very simple way to cut through the noise is to identify the continents and islands that exist in a network, create subgraphs using them, and then analyze and visualize those subgraphs.

These continents and islands are formally...