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

lognormal_pred_kernel(ppmr, beta, sigma)

## Arguments

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

## Value

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

## 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.