In crazycapivara/h3-r: R Bindings for H3

# Sometimes 'ragg' causes problemes when building 'pkgdown' site
# knitr::opts_chunk$set(dev = "png", dev.args = list(type = "cairo-png"))

The package h3 provides R bindings for H3, a hexagonal hierarchical spatial indexing system.

See also H3 Tutorial.

Core Functions

library(h3)

# Index a lat/lng point to an H3 index
coords <- c(37.5, -122.5)
res <- 9

(h3_index <- geo_to_h3(coords, res))

# Get the center of an H3 index as a lat/lng point
h3_to_geo(h3_index)

# Get the vertices of an H3 index as lat/lng points
h3_to_geo_boundary(h3_index)

Usually functions are vectorized:

(coords <- road_safety_greater_manchester[1:2, ])

(h3_indexes <- geo_to_h3(coords, 8))

h3_to_geo_boundary(h3_indexes)

If sf is installed, you can get the polygons of H3 indexes like this:

h3_to_geo_boundary_sf(h3_indexes)

Hierachy

# Get the children of an H3 index at the given (finer) resolution
(res <- h3_get_resolution(h3_index) + 1)
h3_to_children(h3_index, res)

# Get the parent of an H3 index at the given (coarser) resolution
(res <- h3_get_resolution(h3_index) - 1)
h3_to_parent(h3_index, res)

Traversal

# Find all H3 indexes within a given distance from the origin (filled ring)
radius <- 1
k_ring(h3_index, radius)

k_ring_distances(h3_index, radius = 2)

# Get the distance in grid cells between two H3 indexes
h3_distance("8928342e20fffff", "8928342e21bffff")

Regions

# Get the multipolygon (array of polygons) for a set of H3 indexes
h3_indexes <- c("85291a6ffffffff", "85291a6bfffffff", "852834d3fffffff")
h3_set_to_multi_polygon(h3_indexes) %>%
  sf::st_geometry() %>% plot(col = "blue")

Rendering Hexagons

# Binning
h3_index <- geo_to_h3(road_safety_greater_manchester)
tbl <- table(h3_index) %>%
  tibble::as_tibble()
hexagons <- h3_to_geo_boundary_sf(tbl$h3_index) %>%
  dplyr::mutate(index = tbl$h3_index, accidents = tbl$n)
head(hexagons)

# Rendering
library(leaflet)

pal <- colorBin("YlOrRd", domain = hexagons$accidents)

map <- leaflet(data = hexagons, width = "100%") %>%
  addProviderTiles("Stamen.Toner") %>%
  addPolygons(
    weight = 2,
    color = "white",
    fillColor = ~ pal(accidents),
    fillOpacity = 0.8,
    label = ~ sprintf("%i accidents (%s)", accidents, index)
  )

map

crazycapivara/h3-r documentation built on Aug. 10, 2022, 1:17 p.m.