Find small areas for PPR latitudes and longitudes

gps_overlay.r

# Overlay the small areas from the census data
# load small area files - remember this needs to be in GPS form for matching.
map_data <- readShapePoly('Census2011_Small_Areas_generalised20m/small_areas_gps.shp')

# Assign a small area and electoral district to each property with a GPS coordinate.
# The assignment of points to polygons is done using the sp::over() function.
# Inputs are a SpatialPoints (house locations) set, and SpatialPolygons (boundary shapes)
spatial_points <- SpatialPointsDataFrame(coords = ppr_data[!is.na(latitude),.(longitude,latitude)], data=ppr_data[!is.na(latitude), .(input_string, postcode)])
polygon_overlap <- over(spatial_points, map_data)

# Now we can merge the Small Area / Electoral District IDs back onto the ppr_data.
ppr_data[!is.na(latitude), geo_county:=polygon_overlap$COUNTYNAME]
ppr_data$geo_county = str_replace(ppr_data$geo_county, pattern = " County", replacement = "")
ppr_data[!is.na(latitude), electoral_district:=polygon_overlap$EDNAME]
ppr_data[!is.na(latitude), electoral_district_id:=polygon_overlap$CSOED]
ppr_data[!is.na(latitude), region:=polygon_overlap$NUTS3NAME]
ppr_data[!is.na(latitude), small_area:=polygon_overlap$SMALL_AREA]