R/parameters_nat.R
variant_fold_reduction_vector.RdGenerate a vector for each time step where no VFR effect corresponds
to values in the vector of 1, and the appropriate VFR adjustment otherwise.
variant_fold_reduction_vector(parameters, dt, vfr, vfr_time_1, vfr_time_2)a list of model parameters
time step size
a positive value giving the fold reduction
time to begin reduction
time to end reduction