*3.2. Path Length*

In a complex network, the number of edges included in a route between any two points represents the path length of these two points. The average of the shortest path lengths between any two points reflects the size of the network, called the feature path length. If there is no path between the two points, the path length between the two points is infinite.

The length of the feature path is computed by Equation (3). In Equation (3), *l* is the length of the network feature; *N* refers to the number of network nodes; and *dij* is the path length between two points. The maximum path length between all pairs of nodes represents the diameter of the network. The path length and network diameter measure the transmission performance and efficiency of the network.

$$d = \frac{1}{N(N-1)} \sum\_{i \neq j} d\_{ij} \tag{3}$$
