Get the neighbors of a Quadtree cell

Source: R/get_neighbors.R

Returns a matrix with information about the neighbors of a quadtree cell.

# S4 method for Quadtree,numeric
get_neighbors(x, y)

Arguments

x

Quadtree

y

two-element numeric vector; the x and y coordinates of a point - this is used to identify which quadtree cell to find neighbors for.

Value

A six-column matrix with one row per neighboring cell. It has the following columns:

  • id: the ID of the cell

  • xmin, xmax, ymin, ymax: the x and y limits of the cell

  • value: the value of the cell

Note that this return matrix only includes terminal nodes/cells - that is, cells that have no children. Also note that cells that are diagonal from each other are considered to be neighbors.

Examples

library(quadtree)
habitat <- terra::rast(system.file("extdata", "habitat.tif", package="quadtree"))

# create a quadtree
qt <- quadtree(habitat, split_threshold = .1, adj_type = "expand")

# get the cell's neighbors
pt <- c(27000, 10000)
nbs <- get_neighbors(qt, pt)

# plot the neighbors
plot(qt, border_lwd = .3)
points(pt[1], pt[2], col = "black", bg = "lightblue", pch = 21)
with(data.frame(nbs),
   rect(xmin, ymin, xmax, ymax, col = "red", border = "black", lwd = 2))