3. Do graph analysis

A. Execute ST_GraphAnalysis

Weighted

We do the actual graph analysis on connected component 1 as follows:

EXECUTE ST_GraphAnalysis(routes_1.edges, 'weight', 'routes', 3);

Please see the Javadoc for ST_GraphAnalysis (pending) for an explanation of the parameters. The default output table prefix is output.

This produces a table routes.graph_analysis containing

• id The node id
• betweenness_centrality Betweenness centrality
• closeness_centrality Closeness centrality

Underneath the hood, this function uses a modified version of Dijkstra's algorithm to calculate, for a given fixed node, this shortest distance to every other node, as well as the number of shortest paths to every other node.

Unweighted

We could just as easily consider the graph to be unweighted bidirectional:

EXECUTE ST_GraphAnalysis(routes_1.edges, 1, 'routes_unweighted', 3);

B. Recover the node geometries

It remains only to match the node ids with their geometries in routes.nodes (or in routes_1.nodes).