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Convert sf geometry to H3 Cells

Source: R/sfc-to-cells.R
sfc_to_cells.Rd

Given a vector of sf geometries (class sfc) create a list of H3 vectors. Each list element contains the vector of H3 cells that cover the geometry.

Usage

sfc_to_cells(x, resolution, containment = "intersect")

Arguments

x

for h3_from_points() an object of class sfc_POINT. For h3_from_strings() a character vector of H3 index IDs. For h3_from_xy() a numeric vector of longitudes.

resolution

an integer indicating the H3 cell resolution. Must be between 0 and 15 inclusive.

containment

default "intersect". Must be one of "intersect", "centroid", or "boundary". See details.

Value

An H3 vector.

Details

Note, use flatten_h3() to reduce the list to a single vector.

The Containment Mode determines if an H3 cell should be returned.

  • "centroid" returns every cell whose centroid are contained inside of a polygon. This is the fastest option but may not cover the entire polygon.

  • "boundary" this returns the cells which are completely contained by the polygon. Much of a polygon might not be covered using this approach.

  • "intersect" ensures that a polygon is entirely covered. If an H3 cell comes in contact with the polygon it will be returned. This is the default.

  • "contains" behaves the same as "intersect", but also handles the case where the geometry is being covered by a cell without intersecting with its boundaries. In such cases, the covering cell is returned.

Examples

if (interactive() && rlang::is_installed("sf")) {
  nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
  geo <- sf::st_geometry(nc)
  cells <- sfc_to_cells(geo, 5)

  head(cells)

  plot(flatten_h3(cells))
}