Zonal Statistics for Hex Cells

Computes zonal statistics by aggregating all raster pixels falling within each hexagonal cell polygon. More accurate than hex_extract() but slower because it requires polygon geometries.

Usage

hex_zonal(raster, grid, fun = "mean", boundary = NULL, cells = NULL)

Arguments

raster

A terra::SpatRaster object.

grid

A HexGridInfo or HexData object specifying the grid.

fun

Summary function name: "mean" (default), "sum", "min", "max", "sd", or "count".

boundary

Optional sf polygon to limit the analysis extent.

cells

Optional cell IDs. If provided, only these cells are included.

Value

A data.frame with columns cell_id, plus one column per raster layer containing the aggregated values.

Details

Requires the terra package (in Suggests). The function:

1. Generates hex polygon geometries via cell_to_sf()

2. Calls terra::extract(raster, polygons, fun = fun)

3. Joins results back to cell IDs

For point-based extraction (faster, at cell centers only), use hex_extract() instead.

See also

hex_extract() for cell-center extraction, cell_to_sf() for hex polygon generation

Examples

# \donttest{
if (requireNamespace("terra", quietly = TRUE)) {
  r <- terra::rast(nrows = 100, ncols = 100,
                   xmin = -10, xmax = 10, ymin = 40, ymax = 55)
  terra::values(r) <- runif(10000)
  names(r) <- "temperature"

  g <- hex_grid(area_km2 = 500)
  df <- data.frame(lon = c(0, 5), lat = c(45, 50))
  hd <- hexify(df, lon = "lon", lat = "lat", grid = g)
  hex_zonal(r, hd, fun = "mean")
}
# }