  Recurrent events arise frequently in biomedical research, where the subject
may experience the same type of events more than once. The Andersen-Gill (AG)
model has become increasingly popular in the analysis of recurrent events
particularly when the event rate is not constant over time. We propose a
procedure for calculating the power and sample size for the robust Wald test
from the AG model in superiority, noninferiority, and equivalence clinical
trials. Its performance is demonstrated by numerical examples. Sample SAS code
is provided in the Supplementary Material.
