grid_thinning: Perform Grid-Based Thinning of Spatial Points

In GeoThinneR: Efficient Spatial Thinning of Species Occurrences

Perform Grid-Based Thinning of Spatial Points

Description

This function performs thinning of spatial points by assigning them to grid cells based on a specified resolution or thinning distance. It can either create a new raster grid or use an existing 'terra::SpatRaster' object.

Usage

grid_thinning(
  coordinates,
  thin_dist = NULL,
  resolution = NULL,
  origin = NULL,
  raster_obj = NULL,
  n = 1,
  trials = 10,
  all_trials = FALSE,
  crs = "epsg:4326",
  priority = NULL
)

Arguments

coordinates	A numeric matrix or data frame with two columns representing the x (longitude) and y (latitude) coordinates of the points.
thin_dist	A numeric value representing the thinning distance in kilometers. It will be converted to degrees if 'resolution' is not provided.
resolution	A numeric value representing the resolution (in degrees) of the raster grid. If provided, this takes priority over 'thin_dist'.
origin	A numeric vector of length 2 (e.g., 'c(0, 0)'), specifying the origin of the raster grid (optional).
raster_obj	An optional 'terra::SpatRaster' object to use for grid thinning. If provided, the raster object will be used instead of creating a new one.
n	A positive integer specifying the maximum number of points to retain per grid cell (default: 1).
trials	An integer specifying the number of trials to perform for thinning (default: 10).
all_trials	A logical value indicating whether to return results for all trials ('TRUE') or just the first trial ('FALSE', default).
crs	An optional CRS (Coordinate Reference System) to project the coordinates and raster (default WGS84, 'epsg:4326'). This can be an EPSG code, a PROJ.4 string, or a 'terra::crs' object.
priority	A numeric vector of the same length as the number of points, specifying a priority weight for each point. Higher values indicate higher importance and are favored when selecting which points to retain. Priority is used to guide selection when multiple candidate points are otherwise equally valid (e.g., points in the same grid cell, with the same rounded coordinates, or with the same number of neighbors).

Value

A list of logical vectors indicating which points to keep for each trial.

Examples

# Example: Grid thinning using thin_dist
coords <- matrix(c(-122.4194, 37.7749,
                        -122.4195, 37.7740,
                        -122.4196, 37.7741), ncol = 2, byrow = TRUE)

result <- grid_thinning(coords, thin_dist = 10, trials = 5, all_trials = TRUE)
print(result)

# Example: Grid thinning using a custom resolution
result_res <- grid_thinning(coords, resolution = 0.01, n = 2, trials = 5)
print(result_res)

# Example: Using a custom raster object
library(terra)
rast_obj <- terra::rast(nrows = 100, ncols = 100, xmin = -123, xmax = -121, ymin = 36, ymax = 38)
result_raster <- grid_thinning(coords, raster_obj = rast_obj, trials = 5)
print(result_raster)

GeoThinneR documentation built on Nov. 25, 2025, 9:07 a.m.