Returns a data frame representation of a graph. The first two columns represent graph nodes and the third column represents the edge weights between nodes.
All pairwise combinations of subtype1.feats
have an edge weight of 1.
All pairwise combinations of subtype2.feats
have an edge weight of 1.
All pairwise combinations of subtype3.feats
have an edge weight of 1.
All other pairwise combinations have an edge weight uniformly distributed between 0 and 1.