Merge boundary-sharing (in "Rook" contiguity) grids with
fewer target features than the threshold.
This function strongly assumes that the input
is returned from the par_make_grid,
which has "CGRIDID"
as the unique id field.
Arguments
- points_in
sf
orSpatVector
object. Target points of computation.- grid_in
sf
orSpatVector
object. The grid generated bypar_make_grid
.- grid_min_features
integer(1). Threshold to merge adjacent grids.
- merge_max
integer(1). Maximum number of grids to merge per merged set. Default is 4. For example, if the number of grids to merge is 20 and
merge_max
is 10, the function will split the 20 grids into two sets of 10 grids.
References
Polsby DD, Popper FJ. (1991). The Third Criterion: Compactness as a Procedural Safeguard Against Partisan Gerrymandering. Yale Law & Policy Review, 9(2), 301–353. Link
See also
Other Parallelization:
par_cut_coords()
,
par_fallback()
,
par_grid()
,
par_group_grid()
,
par_hierarchy()
,
par_make_grid()
,
par_make_gridset()
,
par_multirasters()
Examples
if (FALSE) {
library(sf)
library(igraph)
library(dplyr)
library(spatstat.random)
dg <- sf::st_as_sfc(st_bbox(c(xmin = 0, ymin = 0, xmax = 8e5, ymax = 6e5)))
sf::st_crs(dg) <- 5070
dgs <- sf::st_as_sf(st_make_grid(dg, n = c(20, 15)))
dgs$CGRIDID <- seq(1, nrow(dgs))
dg_sample <- sf::st_sample(dg, kappa = 5e-9, mu = 15,
scale = 15000, type = "Thomas")
sf::st_crs(dg_sample) <- sf::st_crs(dg)
dg_merged <- par_merge_grid(sf::st_as_sf(dg_sample), dgs, 100)
plot(dg_merged$geometry)
}