Power-law predation kernel

This predation kernel is a power-law, with sigmoidal cut-offs at large and small predator/prey mass ratios.

Usage

power_law_pred_kernel(
  ppmr,
  kernel_exp,
  kernel_l_l,
  kernel_u_l,
  kernel_l_r,
  kernel_u_r
)

Arguments

ppmr

A vector of predator/prey size ratios at which to evaluate the predation kernel.

kernel_exp

The exponent of the power law

kernel_l_l

The location of the left, rising sigmoid

kernel_u_l

The shape of the left, rising sigmoid

kernel_l_r

The location of the right, falling sigmoid

kernel_u_r

The shape of the right, falling sigmoid

Value

A vector giving the value of the predation kernel at each of the predator/prey mass ratios in the ppmr argument.

Details

The return value is calculated as

ppmr^kernel_exp / (1 + (exp(kernel_l_l) / ppmr)^kernel_u_l) / (1 + (ppmr / exp(kernel_l_r))^kernel_u_r)

The parameters need to be given as columns in the species parameter dataframe.

See also

setPredKernel()

Other predation kernel: box_pred_kernel(), lognormal_pred_kernel(), truncated_lognormal_pred_kernel()

Examples

params <- NS_params
# Set all required paramters before changing kernel type
species_params(params)["Cod", "kernel_exp"] <- -0.8
species_params(params)["Cod", "kernel_l_l"] <- 4.6
species_params(params)["Cod", "kernel_u_l"] <- 3
species_params(params)["Cod", "kernel_l_r"] <- 12.5
species_params(params)["Cod", "kernel_u_r"] <- 4.3
species_params(params)["Cod", "kernel_type"] <- "power_law"
plot(w_full(params), getPredKernel(params)["Cod", 10, ], type="l", log="x")