spdep: cell2nb – R documentation

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cell2nb

Generate neighbours list for grid cells

Description

The function generates a list of neighbours for a grid of cells. Helper functions are used to convert to and from the vector indices for row and column grid positions, and rook (shared edge) or queen (shared edge or vertex) neighbour definitions are applied by type. If torus is TRUE, the grid is mapped onto a torus, removing edge effects.

Usage

cell2nb(nrow, ncol, type="rook", torus=FALSE, legacy=FALSE, x=NULL)
vi2mrc(i, nrow, ncol)

Arguments

`nrow`	number of rows in the grid, may also be an object inheriting from class `"SpatialGrid"` or `"GridTopology"` only in `cell2nb`
`ncol`	number of columns in the grid; if `nrow` or `x` is an object inheriting from class `"SpatialGrid"` or `"GridTopology"`, it may be omitted
`type`	default rook, may also be queen
`torus`	default FALSE, if TRUE map grid onto torus
`legacy`	default FALSE, nrow/ncol reversed, if TRUE wrong col/row directions (see https://github.com/r-spatial/spdep/issues/20)
`x`	if given, an object inheriting from class `"SpatialGrid"` or `"GridTopology"`, and replaces `nrow` and `ncol`
`i`	vector of vector indices corresponding to rowcol, a matrix with two columns of row, column indices

Value

The function returns an object of class nb with a list of integer vectors containing neighbour region number ids. See card for details of “nb” objects.

Author(s)

Roger Bivand Roger.Bivand@nhh.no

Examples

nb7rt <- cell2nb(7, 7)
summary(nb7rt)
xyc <- attr(nb7rt, "region.id")
xy <- matrix(as.integer(unlist(strsplit(xyc, ":"))), ncol=2, byrow=TRUE)
plot(nb7rt, xy)
nb7rt <- cell2nb(7, 7, torus=TRUE)
summary(nb7rt)
# https://github.com/r-spatial/spdep/issues/20
GT <- GridTopology(c(1, 1), c(1, 1), c(10, 50))
SPix <- as(SpatialGrid(GT), "SpatialPixels")
nb_rook_cont <- poly2nb(as(SPix, "SpatialPolygons"), queen=FALSE)
nb_rook_dist <- dnearneigh(coordinates(SPix), 0, 1.01)
all.equal(nb_rook_cont, nb_rook_dist, check.attributes=FALSE)
## [1] TRUE
t.nb <- cell2nb(GT, type='rook', legacy=TRUE)
isTRUE(all.equal(nb_rook_cont, t.nb, check.attributes=FALSE))
## [1] FALSE
t.nb <- cell2nb(GT, type='rook')
isTRUE(all.equal(nb_rook_cont, t.nb, check.attributes=FALSE))
## [1] TRUE
# https://github.com/r-spatial/spdep/issues/55
# problem reported in issue caused by rep() cycling in unexpected order
GT <- GridTopology(c(1, 1), c(1, 1), c(22, 11))
SPix <- as(SpatialGrid(GT), "SpatialPixels")
nb_rook_cont <- poly2nb(as(SPix, "SpatialPolygons"), queen=FALSE)
nb_rook_dist <- dnearneigh(coordinates(SPix), 0, 1.01)
all.equal(nb_rook_cont, nb_rook_dist, check.attributes=FALSE)
t.nb <- cell2nb(GT, type='rook', legacy=TRUE)
isTRUE(all.equal(nb_rook_cont, t.nb, check.attributes=FALSE))
## [1] FALSE
t.nb <- cell2nb(GT, type='rook', legacy=FALSE)
isTRUE(all.equal(nb_rook_cont, t.nb, check.attributes=FALSE))
## [1] TRUE

spdep

Spatial Dependence: Weighting Schemes, Statistics

v1.1-11

GPL (>= 2)

Authors

Roger Bivand [cre, aut] (<https://orcid.org/0000-0003-2392-6140>), Micah Altman [ctb], Luc Anselin [ctb], Renato Assunção [ctb], Olaf Berke [ctb], Andrew Bernat [ctb], Guillaume Blanchet [ctb], Eric Blankmeyer [ctb], Marilia Carvalho [ctb], Bjarke Christensen [ctb], Yongwan Chun [ctb], Carsten Dormann [ctb], Stéphane Dray [ctb], Virgilio Gómez-Rubio [ctb], Martin Gubri [ctb], Rein Halbersma [ctb], Elias Krainski [ctb], Pierre Legendre [ctb], Nicholas Lewin-Koh [ctb], Angela Li [ctb], Hongfei Li [ctb], Jielai Ma [ctb], Abhirup Mallik [ctb, trl], Giovanni Millo [ctb], Werner Mueller [ctb], Hisaji Ono [ctb], Pedro Peres-Neto [ctb], Gianfranco Piras [ctb], Markus Reder [ctb], Jeff Sauer [ctb], Michael Tiefelsdorf [ctb], René Westerholt [ctb], Levi Wolf [ctb], Danlin Yu [ctb]

Initial release

2021-09-07