grid_clip: Clip hexagon grid to polygon boundary

In hexify: Equal-Area Hex Grids on the 'Snyder' 'ISEA' 'Icosahedron'

Clip hexagon grid to polygon boundary

Description

Creates hexagon polygons clipped to a given polygon boundary. This is useful for generating grids that conform to country borders, study areas, or other irregular boundaries.

Usage

grid_clip(boundary, grid, crop = TRUE)

Arguments

boundary	An sf/sfc polygon to clip to. Can be a country boundary, study area, or any polygon geometry.
grid	A HexGridInfo object specifying the grid parameters
crop	If TRUE (default), cells are cropped to the boundary. If FALSE, only cells whose centroids fall within the boundary are kept (no cropping).

Details

The function first generates cells covering the boundary polygon, then clips or filters them. For H3 grids, all cells that overlap the boundary are included (not just cells whose center falls inside), ensuring full spatial coverage with no gaps along the boundary edge.

When crop = TRUE, hexagons are geometrically intersected with the boundary, which may produce partial hexagons at the edges. When crop = FALSE, only complete hexagons whose centroids fall within the boundary are returned.

Value

sf object with hexagon polygons clipped to the boundary

See Also

grid_rect for rectangular grids, grid_global for global grids

Examples

# Get France boundary from built-in world map
france <- hexify_world[hexify_world$name == "France", ]

# Create grid clipped to France
grid <- hex_grid(area_km2 = 2000)
france_grid <- grid_clip(france, grid)

# Plot result
library(ggplot2)
ggplot() +
  geom_sf(data = france, fill = "gray95") +
  geom_sf(data = france_grid, fill = alpha("steelblue", 0.3),
          color = "steelblue") +
  theme_minimal()

# Keep only complete hexagons (no cropping)
france_grid_complete <- grid_clip(france, grid, crop = FALSE)

hexify documentation built on March 1, 2026, 1:07 a.m.