as.server.list          Creates a '"server.list"' object from a list of
                        times and starting availability.
as.server.stepfun       Create a 'server.stepfun' object with a roster
                        of times and number of available servers.
average_queue           Compute time average queue length
depart                  get departure times from 'queue_list' object
lag_step                Add lag to vector of arrival times.
plot.queue_list         ggplot2 method for output from queueing model
print.summary_queue_list
                        Print method for output of
                        'summary.queue_list'.
ql_summary              Summarise queue lengths
queue                   Compute the departure times for a set of
                        customers in a queue from their arrival and
                        service times.
queue_lengths           Compute queue lengths from arrival, service and
                        departure data
queue_step              Compute the departure times and queue lengths
                        for a queueing system from arrival and service
                        times.
summary.queue_list      Summary method for queue_list object
wait_step               Compute maximum time for each row from two
                        vectors of arrival times.
