Figure 4.—

Log-scaled degree distribution of the graph created from part of the RAGT R2n grain maize breeding program. In this undirected, unweighted graph, parental inbred lines are represented as vertices and single-cross hybrids as edges. Each dot represents a unique log-scaled vertex degree (horizontal axis) and the log of its frequency in the graph (vertical axis). The red line represents the fitted power law distribution by means of likelihood maximization. The threshold value of 6 was determined by minimizing the Kolmogorov–Smirnov statistic as described by Clauset et al. (2009).