Fig. 3

From the aforementioned relationship between set-cluster contrast \(CC_s\) and relaxed set-cluster contrast \(CC_{rs}\), it can be seen that they differ when the elements of C do not coincide exactly with those of any subtree in \(D_i\). In this example all cluster contrasts yield a zero value (red, blue, and green), except for \(CC_{rs}\) (purple). Both elements of C are part of the elements of the largest subtree in \(D_i\). In fact, both elements of C belong to the largest subtree in N, \(CC_{rs}(C,D_i)\) being equal to 2/3 (purple)