trophic: Calculate mean trophic level
In turf-reserves/mpa.tools: Tools to simulate and analyze no-take Marine Reserves

Calulates mean trophic level, by year, site, and transect, for a given location.

1	trophic(data, location)

`data`	A dataframe that contains at least columns of Ano, Zona (e.g. "Zona de pesca" or "Zona de no pesca"), Sitio, Transecto, GeneroEspecie, and Abundancia. A column for trophic level is optional, though heavily suggested to avoid errors in calculations (this package might not have trophic level information for all species).
`location`	A quoted string that indicates the location.
`tl`	An optional dataframe with a column for each species (called GenusSpecies) and a column for the trophic level of each species (called TL).