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Adjacent cells or polygons

adjacent.Rd

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

Usage

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

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

Arguments

x

SpatRaster, or SpatVector of polygons

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

Note

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

See also

relate, nearby, nearest

Value

matrix

Examples

r <- rast(nrows=10, ncols=10)
adjacent(r, cells=c(1, 5, 55), directions="queen") 
#>    [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#> 0   NaN  NaN  NaN   10    2   20   11   12
#> 4   NaN  NaN  NaN    4    6   14   15   16
#> 54   44   45   46   54   56   64   65   66
r <- rast(nrows=10, ncols=10, crs="+proj=utm +zone=1 +datum=WGS84")
adjacent(r, cells=11, directions="rook") 
#>    [,1] [,2] [,3] [,4]
#> 10    1  NaN   12   21

#same as 
rk <- matrix(c(0,1,0,1,0,1,0,1,0), 3, 3)
adjacent(r, cells=11, directions=rk) 
#>    [,1] [,2] [,3] [,4]
#> 10    1  NaN   12   21

## 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") 
#>    [,1] [,2] [,3] [,4]
#> 10    1   20   12   21

f <- system.file("ex/lux.shp", package="terra")
v <- vect(f)
a <- adjacent(v, symmetrical=TRUE)
head(a)
#>      from to
#> [1,]    1  2
#> [2,]    1  4
#> [3,]    1  5
#> [4,]    2  3
#> [5,]    2  4
#> [6,]    2  5