Calculate the midpoint collection time of the maximum excretion rate

Usage

pk.calc.ertmax(
  conc,
  volume,
  time,
  duration.conc,
  options = list(),
  check = TRUE,
  first.tmax = NULL
)

conc: The concentration in the excreta (e.g., urine or feces)
volume: The volume (or mass) of the sample
time: The starting time of the collection interval
duration.conc: The duration of the collection interval
options: List of changes to the default PKNCA options (see PKNCA.options())
check: Should the concentration and time data be checked?
first.tmax: If TRUE, return the first time of maximum excretion rate; otherwise, return the last

The midpoint collection time of the maximum excretion rate, or NA if not available