This function applies a brute force algorithm to thin a set of spatial coordinates, attempting to maximize the number of points retained while ensuring a minimum distance (`thin_dist`) between any two points.
Usage
brute_force_thinning(
coordinates,
thin_dist = 10,
trials = 10,
all_trials = FALSE,
target_points = NULL,
euclidean = FALSE,
R = 6371
)Arguments
- coordinates
A numeric matrix or data frame with two columns representing longitude and latitude (or XY coordinates if `euclidean = TRUE`).
- thin_dist
Numeric value representing the thinning distance in kilometers (default: 10 km).
- trials
Integer specifying the number of trials to run for thinning (default: 10).
- all_trials
Logical value indicating whether to return the results of all trials (`TRUE`) or just the best attempt with the most points retained (`FALSE`, default).
- target_points
Optional integer specifying the number of points to retain. If `NULL` (default), the function tries to maximize the number of points retained.
- euclidean
Logical value indicating whether to compute the Euclidean distance (`TRUE`) or Haversine distance (`FALSE`, default).
- R
Numeric value representing the Earth's radius in kilometers (default: 6371 km). Only used if `euclidean = FALSE`.
Value
A logical vector indicating which points are kept in the best trial if `all_trials = FALSE`; otherwise, a list of logical vectors for each trial.
Examples
# Example with geographic coordinates (Haversine distance)
coords <- data.frame(
long = c(-122.4194, -122.4195, -122.4196),
lat = c(37.7749, 37.7740, 37.7741)
)
coords <- as.matrix(coords)
result <- brute_force_thinning(coords, thin_dist = 0.1, trials = 5)
print(result)
#> [[1]]
#> [1] TRUE TRUE FALSE
#>
# Example computing Euclidean distance
result_euclidean <- brute_force_thinning(coords, thin_dist = 1, trials = 5, euclidean = TRUE)
print(result_euclidean)
#> [[1]]
#> [1] FALSE FALSE TRUE
#>