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Create supercells as points

Source: R/sc_slic_points.R
sc_slic_points.Rd

Runs the SLIC workflow and returns supercell centers as points. Use iter = 0 to return the initial centers before iterations. For polygon outputs, use sc_slic(); for raster output, use sc_slic_raster() By default, returns the same fields as sc_slic(): outcomes = c("supercells", "coordinates", "values"). Use outcomes = "values" for value summaries only.

Usage

sc_slic_points(
  x,
  step = NULL,
  compactness,
  dist_fun = "euclidean",
  avg_fun = "mean",
  clean = TRUE,
  minarea,
  iter = 10,
  k = NULL,
  centers = NULL,
  outcomes = c("supercells", "coordinates", "values"),
  chunks = FALSE,
  verbose = 0
)

Arguments

x

An object of class SpatRaster (terra) or class stars (stars).

step

Initial center spacing (alternative is k). Provide a plain numeric value for cell units, or use use_meters() for map-distance steps in meters (automatically converted to cells using raster resolution).

compactness

A compactness value. Use sc_tune_compactness() to estimate it. Use use_adaptive() to enable adaptive compactness based on local feature-space distances.

dist_fun

A supported distance name from sc_list_distances() or a custom function that takes two numeric vectors and returns one finite, nonnegative value. Smaller values must mean greater similarity.

avg_fun

An averaging function name or custom function used to summarize values within each supercell. Supported names: "mean" and "median". A custom function must accept a numeric vector and return a single numeric value.

clean

Should connectivity of the supercells be enforced?

minarea

When clean = TRUE, connected components containing minarea cells or fewer are merged into an adjacent component. If minarea is omitted or set to 0, the threshold is selected automatically as one quarter of the raster cell count divided by the number of initialized centers: floor(ncell / (4 * n_centers)).

iter

Number of iterations.

k

The number of supercells desired (alternative to step).

centers

Optional sf object of custom centers. Requires step.

outcomes

Character vector controlling which fields are returned. Allowed values are "supercells", "coordinates", and "values". Default is full output (c("supercells", "coordinates", "values")). Use outcomes = "values" for value summaries only.

chunks

Chunking option. Use FALSE for no chunking, TRUE for automatic chunking based on size, or a numeric value for a fixed chunk size (in number of cells per side).

verbose

Verbosity level.

Value

An sf object with supercell center points and summary statistics

See also

sc_slic(), sc_slic_raster()

Examples

library(supercells)
vol = terra::rast(system.file("raster/volcano.tif", package = "supercells"))

# initial centers (only after local minima placement, no iterations)
init_pts = sc_slic_points(vol, step = 12, compactness = 1, iter = 0)
terra::plot(vol)
plot(sf::st_geometry(init_pts), add = TRUE, pch = 3, col = "red")


# final supercell centers
vol_pts = sc_slic_points(vol, step = 12, compactness = 1)
terra::plot(vol)
plot(sf::st_geometry(vol_pts), add = TRUE, pch = 16, col = "red")