StoppingTargetProb-class: Stop based on probability of target tox interval
In 0liver0815/onc-crmpack-test: Object-Oriented Implementation of CRM Designs

Stop based on probability of target tox interval

target: the target toxicity interval, e.g. c(0.2, 0.35)
prob: required target toxicity probability (e.g. 0.4) for reaching sufficient precision

# As example, here is the rule for: 
#   stopping the study if the posterior probability that [0.2 =< Prob(DLT | dose) <= 0.35] 
#   for the next best dose is above 0.5

myStopping <- StoppingTargetProb(target=c(0.2, 0.35),
                                 prob=0.5)