Merges overlapping spells for the same (head, tail) pair into a single
row. Useful when concatenating cumulative edgelists across multiple
simulations or sources, where the same partnership can appear in more
than one segment. The reachability functions assume non-overlapping
input.
See also
as_cumulative_edgelist() for one source of duplicates;
get_forward_reachable() / get_backward_reachable(), which expect
non-overlapping input.
Other cumulative_edgelist:
as_cumulative_edgelist(),
get_cumulative_degree(),
get_cumulative_edgelist(),
get_cumulative_edgelists_df(),
get_partners(),
reachable-nodes,
update_cumulative_edgelist()