Associations are shown with cluster indices, which summarize properties of clusters derived from affinity propagation clusters of the TIL map--properties that provide details on local structure beyond simple densities. The Ball-Hall index is a particular clustering index, summarizing the mean, through all the clusters, of their mean dispersion and is equivalent to the mean of the squared distances of the points of the cluster with respect to its center. In our data, the Ball-Hall index is correlated (ρSpearman 0.95) with the mean cluster extent, CE. Significance test p value is shown in the lower left. The Banfield-Raftery index is the weighted sum of the logarithms of the mean cluster dispersion and, in our data, often correlates with the number of clusters.