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)

ppmr | A vector of predator/prey size ratios |
---|---|

beta | The preferred predator/prey size ratio |

sigma | The width parameter of the log-normal kernel |

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

argument.

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.