Deterministic multistage Beverton-Holt model using nested for loops in R

NestedForLoop.R

years = 30
prop_female = 0.5
egg_surv = 0.6

fecundity = c(0, 0, 200, 400, 800)
survival = c(0.2, 0.4, 0.6, 0.8, 0)
capacity = c(1e6, 1e5, 1e4, 1e3, 1e2)

beverton_holt <- function(N, p, c){
  N / ((1/p) + (N/c))
}  

results = matrix(data = 0, nrow = years, ncol = length(fecundity))
results[1,] = 10

for (i in 1:(nrow(results) - 1)){
  for (j in 1:(ncol(results))){ 
    N = results[i,j]
    fec_age_j = fecundity[j]
    surv_age_j = survival[j]
    # spawning
    if (fec_age_j > 0){
      spawn_age_j = N * prop_female
      results[i+1, 1] = results[i+1, 1] + beverton_holt(spawn_age_j, fec_age_j * egg_surv, capacity[1] - results[i+1, 1])
    }
    # survival
    if (surv_age_j > 0){
      results[i+1, j+1] = results[i+1, j+1] + beverton_holt(N, surv_age_j, capacity[j+1] - results[i+1, j+1])
    }
  }
}
results