Figure 1.

Second-order (k = 2) nearest neighbor relationships for a set of six point locations. Arrows indicate point-pairs that are second-order nearest neighbors of one another. For example the arrow from point 1 to point 2 indicates that point 2 is the second nearest neighbor to point 1. The double-headed arrow between points 2 and 4 indicates they are second-order nearest neighbors of one another. Point 2 has the highest leverage since it is the most "connected" by second-order weights.