Combined statistical areas are "two or more adjacent CBSAs that have significant employment interchanges." In turn, CSAs are composed of multiple metropolitan and/or micropolitan areas, and should not be compared with individual core-based statistical areas.
combined_statistical_areas(cb = FALSE, resolution = "500k", year = NULL,
...)If cb is set to TRUE, download a generalized (1:500k) cartographic boundary file. Defaults to FALSE (the most detailed TIGER/Line file).
The resolution of the cartographic boundary file (if cb == TRUE). Defaults to '500k'; options include '5m' (1:5 million) and '20m' (1:20 million).
the data year (defaults to 2016).
arguments to be passed to the underlying `load_tiger` function, which is not exported.
Options include refresh, which specifies whether or not to re-download shapefiles
(defaults to FALSE).
http://www2.census.gov/geo/pdfs/maps-data/data/tiger/tgrshp2015/TGRSHP2015_TechDoc.pdf
Other metro area functions: core_based_statistical_areas,
metro_divisions, new_england,
urban_areas