Draw time to event (tte) from a Poisson or Poisson-Gamma (PG) Mixture/Negative Binomial (NB) Process

Usage

rpoisgamma(
  n,
  rate,
  theta = NULL,
  obs_time = 1,
  t_reps,
  seed = NULL,
  return_ind_rate = FALSE,
  return_df = FALSE
)

Arguments

n: The number of observations to be drawn
rate: rate of the event (in terms of events per observation-time)
theta: Optional. When omitted, the function simulates times for a Poisson process. Represents the shape of the gamma mixture distribution. Estimated and reported as theta in negative binomial regression analyses in r.
obs_time: period over which events are observable
t_reps: Optional. Number of TBEs to be generated to capture events within the observation window. When omitted, the function sets t_reps to the 99.99th quantile of the Poisson (if no theta is provided) or negative binomial (if theta is provided). Thus, the risk of missing possible events in the observation window is 0.01%.
seed: An integer which will be used to set the seed for this draw.
return_ind_rate: A boolean that indicates whether an additional vector with the rate parameters used per observation is used. It will alter the structure of the results to two lists, one storing tte with name tte, and the other with name ind_rate
return_df: A boolean that indicates whether a data.table object should be returned

Value

Estimate(s) from the time to event based on poisson/Poisson-Gamma (PG) Mixture/Negative Binomial (NB) distribution based on given parameters

Details

Function to simulate event times from a Poisson or Poisson-Gamma (PG) Mixture/Negative Binomial (NB) Process Event times are determined by sampling times between events (TBEs) from an exponential distribution, and cumulating these to derive the event times. Events occurring within the set observation time window are retained and returned. For times for a Poisson process, the provided rate is assumed constant. For a PG or NB, the individual rates are sampled from a Gamma distribution with shape = theta and scale = rate/theta.

Examples

rpoisgamma(1,rate=1,obs_time=1,theta=1)
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