lognormal_pred_kernel: Lognormal predation kernel

In mizer: Dynamic Multi-Species Size Spectrum Modelling

Lognormal predation kernel

Description

This is the most commonly-used predation kernel. The log of the predator/prey mass ratio is normally distributed.

Usage

lognormal_pred_kernel(ppmr, beta, sigma)

Arguments

ppmr	A vector of predator/prey size ratios
beta	The preferred predator/prey size ratio
sigma	The width parameter of the log-normal kernel

Details

Writing the predator mass as w and the prey mass as w_p, the feeding kernel is given as

\phi_i(w, w_p) = \exp \left[ \frac{-(\ln(w / w_p / \beta_i))^2}{2\sigma_i^2} \right]

if w/w_p is larger than 1 and zero otherwise. Here \beta_i is the preferred predator-prey mass ratio and \sigma_i determines the width of the kernel. These two parameters need to be given in the species parameter dataframe in the columns beta and sigma.

This function is called from setPredKernel() to set up the predation kernel slots in a MizerParams object.

Value

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

See Also

setPredKernel()

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

Examples

params <- NS_params
plot(w_full(params), getPredKernel(params)["Cod", 10, ], type="l", log="x")
# The restriction that the kernel is zero for w/w_p < 1 is more
# noticeable for larger sigma
species_params(params)$sigma <- 4
plot(w_full(params), getPredKernel(params)["Cod", 10, ], type="l", log="x")

mizer documentation built on Oct. 17, 2024, 9:07 a.m.