raster (version 1.9-27)

adjacent: Adjacent cells

Description

Identify cells that are adjacent to a set of cells on a raster. See adjacency for an alternative implementation.

Usage

adjacent(x, cells, directions=4, pairs=FALSE, target=NULL, sorted=FALSE)

Arguments

x

Raster* object

cells

vector of cell numbers for which adjacent cells should be found

directions

the number of directions in which cells should be connected: 4 (rook's case), 8 (queen's case), 16, or 'bishop'. Or a neigborhood matrix (see Details)

pairs

Boolean. If TRUE, a matrix of pairs of adjacent cells is returned. If FAlSE, a vector of cells adjacent to from is returned (perhaps intersected with to)

target

optional vector of target cell numbers that should be considered. All other adjacent cells are ignored

sorted

Boolean. Should the results be sorted?

Value

• matrix or vector with adjacent cells.

Details

A neighborhood matrix indentifies the cells around each cell that are considered adjacent. The matrix should have one, and only one, cell with value 0 (the focal cell); at least one cell with value 1 (the adjacent cell(s)); All other cells are not considered adjacent and ignored. Cell numbers start with 1 in the upper-left corner and increase from left to right and from top to bottom.

See Also

adjacency

Examples

r <- raster(nrows=10, ncols=10)
adjacent(r, cells=c(1, 55), directions=8, pairs=TRUE) 

a <- adjacent(r, cell = c(1,55,90), directions=4, sorted=TRUE) 
a

r[c(1,55,90)] <- 1
r[a] <- 2
plot(r)

# same result as above
rook <- matrix(c(NA, 1, NA, 
                  1, 0,  1, 
                 NA, 1, NA), ncol=3, byrow=TRUE)

adjacent(r, cells = c(1,55,90), directions=rook, sorted=TRUE)