Fig. 2From: The Bourque distances for mutation trees of cancersIllustration of the gNNI operation on labeled trees. A On a unrooted labeled tree, a gNNI operation on an edge (a, b) interchanges one or more children of a with an arbitrary number of children of b. B On a rooted labeled tree, a gNNI operation on an edge (a, b) (where b is the child of a) not only rewires the selected edges leaving a and b (left), but also rewires the unique edge entering a and b simultaneously if necessary (right).Back to article page