Get a collection of areas

Get a collection of areas defined by a level and nested within a collection of higher level area(s).

get_area_collection(areas, level = NULL, area_scope = NULL)

Arguments

areas

Data frame representing a valid area hierarchy.

level

The level to return area collection

area_scope

area_ids to subset return level, possible a vector.

Details

This function recursively expands the area hierarchy to identify all areas in area_level level which are nested within areas defined by area_scope.

If level = NULL areas are returned at the lowest level of the hierarchy. An error is thrown if level is not reflected in the hierarchy.

If area_scope = NULL all areas at area_level level are returned. In this case the recursion is shortcut and simply filters the hierarchy to the desired level for efficiency, but it is equivalent to initialising the recursion at the highest level of the hierarchy.

If area_scope is not null, a column area_scope is returned indicating the area in which each returned area is nesteed. area_scope can accept a vector of area_ids and they do not have to be at the same level. If the level of an area in area_scope is higher than area_level level, nothing is returned. An error is thrown if any area_scope are not recognized.

TODO: Should be an example - where is demo_areas, demo_area_geom? data(demo_areas, demo_area_geom)

areas <- get_area_collection(demo_areas, level = 3, area_scope = c("MWI.1", "MWI.3.5")) areas %>% left_join(demo_area_geom %>% filter(type == "boundary")) %>% sf::st_as_sf() %>% ggplot() + geom_sf()