Uses the heuristic from the original Mapper paper to cut a given hierarchical cluster tree at the threshold corresponding to the first empty of a histogram of the linkage distances.
cutoff_first_bin(hcl, diam, num_bins)
hierarchical clustering in the form an 'hclust' object.
largest pairwise distance between the objects used to create the hierarchy.
Controls how many bins there are in the histogram used to determine cutoff.