FIGURE 2.

An illustrative example of clustering analysis using two criteria. The nodes A, B, C, and D represent viruses isolated from humans. The d_g on each edge connecting two nodes represents the genetic distance between corresponding viruses. The d_t on each edge represents the sampling time interval between the corresponding viruses. This example uses 0.02 as clustering threshold for genetic distance and 7 days for sampling time interval. A solid line represents a pair of viruses satisfying both criteria. A dashed line represents a pair of viruses satisfying only the criteria for genetic distance. A dash-dot line represents a pair of viruses satisfying only the criteria for sampling time interval. A dotted line represents a pair of viruses which does not satisfy with any of the criteria.