accumulate              Split-Apply-Combine with Collapsing Groups
csh_from_digits         Derive collapsing scheme from hierarchical
                        classification
frac_complete           Demand minimal fraction of complete records
from_validator          Use a validate::validator object to test a
                        group
min_complete            Demand minimal number of complete records
min_records             Demand minimal number of functons
producers               synthetic data on producers
smoke_test              Test your testing function for common edge
                        cases
