Dendrograms for the two-dimensional scatter plots of Figure 1. There is one-to-one correspondence between the six panels (A-F) of the two figures. Similar dendrograms for the one-dimensional (individual genes) projections of the scatter plots (not shown) are also needed for the evaluation of synergy. The leaves represent samples color-coded as red for cancer and green for health. For each dendrogram, a horizontal line defines a partition into clusters. In A and B there is perfect classification via partition into two and four homogeneous clusters, respectively. In c there is random assignment of samples resulting in inhomogeneity in each cluster and inability to classify. In D, E, F, the outcomes are the same as in A, B, C, respectively, except that the edges of the dendrogram fully connect the root with the leaves and any distance of the horizontal from the leaves will produce the same partition.