aspm.r

File contents

# aspm.r
# aspm: Performs forward simulation of populations, given values of parameters
aspm<-function(Fvec,Rvec,totyrs,M,w){
  Yhat<-NULL
  Bhat<-NULL
  Rtemp<-Rvec[1]
  #N0<-Ninit                       # First start-of-year stock size - fixed
  #N0<-Rtemp*exp(-cumsum(c(0,M[1:(length(M)-1)])))  # initial start-of-year stock size - equil.
  N0<-aveRecr*exp(-cumsum(c(0,M))[1:g]) # better: first only true ages
  N0<-c(N0,aveRecr*exp(-g*M[g+1])/(1-exp(-M[g+1])))# then append the plus group
  for(year in 1:totyrs){
    baseF<-Fvec[year]              # Base fishing mortality
    F0<-baseF*selpat               # Fishing mortality during the year
    C<-(F0/(F0+M))*(1-exp(-(F0+M)))*N0
    Ytemp<-sum(C*w)                    # Total landings
    Ntemp<-N0*exp(-F0-M)           # Forw proj - gives ages 2:(g+1)
    Noldest<-Ntemp[g]+Ntemp[g+1]   # Allow for plus-group
    #print(Ytemp)
    Yhat<-c(Yhat,Ytemp)
    Bhat<-c(Bhat,sum(N0*w))
    Rtemp<-Rvec[year]
    N1<-c(Rtemp,Ntemp[1:(g-1)],Noldest)# Set up stock at end of year
    N0<-N1                         # Prepare for next round
  }
  return(list(Yhat=Yhat,Bhat=Bhat))
}