Calculates the exact one stage Phase II design
ph2single(pu,pa,ep1,ep2,nsoln=5)unacceptable response rate
response rate that is desirable
threshold for the probability of declaring drug desirable under p0
threshold for the probability of rejecting the drug under p1
number of designs with given alpha and beta
ph2single returns a data frame with variables: n, r, and the Type I and Type II errors.