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# Copyright 2001-2010 by Roger Bivand
#
tri2nb <- function(coords, row.names = NULL) {
# require("tripack")
# require("deldir")
if (inherits(coords, "SpatialPoints")) {
if (!is.na(is.projected(coords)) && !is.projected(coords)) {
warning("tri2nb: coordinates should be planar")
}
coords <- coordinates(coords)
}
n <- nrow(coords)
if (n < 3) stop("too few coordinates")
# left <- function(x) {
# res <- (x[3,1]-x[2,1])*(x[1,2]-x[2,2]) >=
# (x[1,1]-x[2,1])*(x[3,2]-x[2,2])
# res
# }
# if (left(coords[1:3,])) stop("first three coordinates collinear")
if (!is.null(row.names)) {
if(length(row.names) != n)
stop("row.names wrong length")
if (length(unique(row.names)) != length(row.names))
stop("non-unique row.names given")
}
if (is.null(row.names)) row.names <- as.character(1:n)
stopifnot(!anyDuplicated(coords))
# tri <- tri.mesh(x=coords[,1], y=coords[,2])
tri <- deldir::deldir(x=coords[,1], y=coords[,2])
from <- c(tri$delsgs[,5], tri$delsgs[,6])
to <- c(tri$delsgs[,6], tri$delsgs[,5])
df <- data.frame(from=as.integer(from), to=as.integer(to), weight=1)
attr(df, "n") <- tri$n.data
class(df) <- c(class(df), "spatial.neighbour")
df1 <- df[order(df$from),]
nb <- sn2listw(df1)$neighbours
# nb <- neighbours(tri)
attr(nb, "region.id") <- row.names
class(nb) <- "nb"
attr(nb, "tri") <- TRUE
attr(nb, "call") <- match.call()
nb <- sym.attr.nb(nb)
nb
}
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