R function for carrying out discrete stochastic simulations of the logistic population model. http://cnr.lwlss.net/DiscreteStochasticLogistic/ #R #Rstats #discrete #stochastic #logistic

simDSLogistic.R

simDSLogistic=function(K,r,N0){
  # Unusually, for this model, we know the number of events a priori
  eventNo=K-N0
  # So we can just generate all required random numbers (quickly) in one go
  unifs=runif(eventNo)
  # Every event produces one cell and consumes one unit of nutrients
  clist=(N0+1):K
  # Simulate time between events by generating 
  # exponential random numbers using the inversion method
  dts=-log(1-unifs)/(r*clist*(1-clist/K))
  return(data.frame(t=c(0,cumsum(dts)),c=c(N0,clist)))
}