Calculate steady-state population structure

Calculates population dynamics over time until a steady state is reached. The steady state is defined as a constant sex–age cohort structure over time, with population size potentially growing or declining at a constant rate. Tracks sex–age cohort structure and population growth based on survival, offtake, and fecundity parameters.

Usage

calc_steady_state_structure(
  initial_herd_structure,
  max_simulation_years,
  min_lambda_change,
  fecundity_female,
  fecundity_male,
  probability_death,
  probability_offtake,
  probability_growth
)

Arguments

initial_herd_structure: Named numeric vector of length 6. Initial number of individuals in each of the 6 sex-age classes used to bootstrap the steady-state simulation (# heads). These values are used as starting points for the iterative simulation and do not affect the final steady-state results (only convergence speed). Must be named with: FJ, FS, FA, MJ, MS, MA.
max_simulation_years: Numeric. Maximum number of years to simulate (years).
min_lambda_change: Numeric. Convergence threshold for changes in cohort-specific growth rates of sex–age cohort proportions (lambda). Iterations of the herd simulation stop when the absolute change in lambda between successive iterations falls below this threshold.
fecundity_female: Numeric. Daily number of female offspring per adult female (# offspring/day)
fecundity_male: Numeric. Daily number of male offspring per adult female (# offspring/day)
probability_death: Named numeric vector of length 10. Probability of animal dying within the model time interval for 10 cohorts (fraction) (cohorts= FB: Female Birth, FJ: Female Juvenile, FS: Female Sub-adult, FA: Female Adult, FC: Female Culling, MB: Male Birth, MJ: Male Juvenile, MS: Male Sub-adult, MA: Male Adult, MC: Male Culling).
probability_offtake: Named numeric vector of length 10. Probability that an animal will be removed from the herd within the model time interval for 10 cohorts (fraction). (cohorts= FB: Female Birth, FJ: Female Juvenile, FS: Female Sub-adult, FA: Female Adult, FC: Female Culling, MB: Male Birth, MJ: Male Juvenile, MS: Male Sub-adult, MA: Male Adult, MC: Male Culling).
probability_growth: Named numeric vector of length 10. Probability of growing into the next age class for 10 cohorts (fraction) (cohorts= FB: Female Birth, FJ: Female Juvenile, FS: Female Sub-adult, FA: Female Adult, FC: Female Culling, MB: Male Birth, MJ: Male Juvenile, MS: Male Sub-adult, MA: Male Adult, MC: Male Culling).

Value

A named list with:

days_to_steady_state: Numeric. Number of days required for the herd population structure to converge to a steady state, defined as the point at which successive iterations produce negligible changes in cohort proportions (days)
herd_structure: Named numeric vector of length 8. Final steady-state share of each of 8 sex-age cohorts (FB, FJ, FS, FA, MB, MJ, MS, MA) (fraction). Shares should sum to 1.
cohort_share: Named numeric vector of length 6. Final steady-state share of 6 grouped sex-age cohorts (FJ, FS, FA, MJ, MS, MA, where FJ = FB + FJ and MJ = MB + MJ) (fraction). Shares should sum to 1.
growth_rate_herd: Numeric. Annualized growth rate at which the herd reaches steady state (fraction)

This function is part of the run_demographic_herd_module().

Usage

Arguments

Value

See also