adjacent: Adjacent cells
In rspatial/terra: Spatial Data Analysis

adjacent

R Documentation

Adjacent cells

Description

Identify cells that are adjacent to a set of raster cells. Or identify adjacent polygons

Usage

## S4 method for signature 'SpatRaster'
adjacent(x, cells, directions="rook", pairs=FALSE, include=FALSE, symmetrical=FALSE)

## S4 method for signature 'SpatVector'
adjacent(x, type="rook", pairs=TRUE, symmetrical=FALSE)

Arguments

`x`	SpatRaster
`cells`	vector of cell numbers for which adjacent cells should be found. Cell numbers start with 1 in the upper-left corner and increase from left to right and from top to bottom
`directions`	character or matrix to indicated the directions in which cells are considered connected. The following character values are allowed: "rook" or "4" for the horizontal and vertical neighbors; "bishop" to get the diagonal neighbors; "queen" or "8" to get the vertical, horizontal and diagonal neighbors; or "16" for knight and one-cell queen move neighbors. If `directions` is a matrix it should have odd dimensions and have logical (or 0, 1) values
`pairs`	logical. If `TRUE`, a two-column matrix of pairs of adjacent cells is returned. If `x` is a `SpatRaster` and `pairs` is `FALSE`, an `n*m` matrix is returned where the number of rows `n` is `length(cells)` and the number of columns `m` is the number of neighbors requested with `directions`
`include`	logical. Should the focal cells be included in the result?
`type`	character. One of "rook", "queen", "touches", or "intersects". "queen" and "touches" are synonyms. "rook" exclude polygons that touch at a single node only. "intersects" includes polygons that touch or overlap
`symmetrical`	logical. If `TRUE` and `pairs=TRUE`, an adjacent pair is only included once. For example, if polygon 1 is adjacent to polygon 3, the implied adjacency between 3 and 1 is not reported

Value

matrix

Note

When using global lon/lat rasters, adjacent cells at the other side of the date-line are included.

Examples

r <- rast(nrows=10, ncols=10)
adjacent(r, cells=c(1, 5, 55), directions="queen") 
r <- rast(nrows=10, ncols=10, crs="+proj=utm +zone=1 +datum=WGS84")
adjacent(r, cells=11, directions="rook") 

#same as 
rk <- matrix(c(0,1,0,1,0,1,0,1,0), 3, 3)
adjacent(r, cells=11, directions=rk) 

## note that with global lat/lon data the E and W connect
r <- rast(nrows=10, ncols=10, crs="+proj=longlat +datum=WGS84")
adjacent(r, cells=11, directions="rook") 

f <- system.file("ex/lux.shp", package="terra")
v <- vect(f)
a <- adjacent(v, symmetrical=TRUE)
head(a)

rspatial/terra documentation built on Nov. 5, 2024, 5:13 p.m.