Add lookup function for census block groups

[mhweber]

Create an sc_get_block groups function to return block groups touching a catchment (watershed? riparian buffer?) and vice-versa? simply build staged lookup table or generate dynamically? We may want to have as a AOI in the API rather than a package function

[jbousquin]

Not sure how far into this you are but some base urls I've used in python in the past that might be useful starting place:
"https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/Tracts_Blocks/MapServer"
from tigris:
"https://www2.census.gov/geo/tiger/GENZ/shp/cb__<state_fip>_bg_500k.zip"
"https://www2.census.gov/geo/tiger/TIGER/BG/"

[mhweber]

@jbousquin - thanks for the urls - hope to work on this over coming month

[katroeder]

Seconding this request. I'd like to pair catchment polygons from StreamCat with census tracts (block groups, etc.) so that I can pull census data from tigris (or other sources with the same census tract IDs) and calculate averages by catchment. It would be amazing if the pairing function had the ability to calculate weighted averages for catchments with partial census tracts in their area, too.

Right now, I'm using sf::st_intersect() & related functions to manually identify which census objects in a given area are within particular catchments (and which catchments are within particular watersheds). It's incredibly inefficient, but it gives me a lookup table of relationships between census objects, catchments, and watersheds, so I can integrate data from different sources.