This function checks which admin levels are in a generalized a data frame formatting like travel_data_sim and
returns the lowest admin unit.
get_admin_level(data)
| data | generalized data frame described in  | 
|---|
integer
Other utility: 
get_beta_params(),
get_gamma_params(),
get_pop_vec(),
get_unique_coords(),
get_unique_ids()
John Giles
get_admin_level(travel_data_sim)#> [1] 2