polygon-to-h3

polygon-to-h3.R

# get the h0 hexes covering a polygon. 


library(duckdbfs)
library(dplyr)
library(sf)
library(spData)

duckdbfs::load_h3()
duckdbfs::load_spatial()



tmp <- tempfile(fileext = ".fgb")
bounds <- spData::us_states |>  dplyr::filter(NAME == "Arizona") |> st_transform(4326) |> write_sf(tmp, append = FALSE)

tmp2 <- tempfile(fileext = ".fgb")
world |> filter(iso_a2 == "US") |> write_sf(tmp2, append = FALSE)

subset <- 
open_dataset(tmp2) |>
  mutate(poly = array_extract(unnest(st_dump(geom)),"geom"),
         hexid = h3_polygon_wkt_to_cells(poly,4L), # must be small enough?
         hexid = unnest(hexid)
        ) |>
  mutate(h0 = h3_h3_to_string( h3_cell_to_parent(hexid, 0L)),
         hexid = h3_h3_to_string (hexid) ) |>
  select(h0) |>
  distinct() |>
  pull(h0)