Food-web specific measures

Measures of trophic level

These measure work by counting the distance to a primary producer -- where "primary producer" is defined as the fact of not having outgoing interactions. Primary producers have a trophic level of 1, and species that consume primary producers have trophic levels of 2, etc. This represents a species' fractional trophic level.

~~~@docs fractional_trophic_level

Because some species higher-up the food chain eat preys at various fractional
trophic levels, there is also a more integrative measure -- the trophic level of
a species is the weighted average of the fractional trophic level of its preys:

~~~@docs
trophic_level

Measures of trophic positions

For every species in a food web, this will return an array with its overall position:

~~~@docs foodweb_position ~~~