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# Copyright 2001-6 by Nicholas Lewin-Koh and Roger S. Bivand.
#
graph2nb <- function(gob, row.names=NULL,sym=FALSE) {
if (!inherits(gob, "Graph")) stop("Not a Graph object")
res <- vector(mode="list", length=gob$np)
if (!is.null(row.names)) {
if(length(row.names) != gob$np)
stop("row.names wrong length")
if (length(unique(row.names)) != length(row.names))
stop("non-unique row.names given")
}
if (gob$np < 1) stop("non-positive gob$np")
if (is.null(row.names)) row.names <- as.character(1:gob$np)
if(sym){
for (i in 1:gob$np) {
res[[i]] <- sort(unique(c(gob$to[gob$from==i],
gob$from[gob$to==i])))
if(length(res[[i]]) == 0L) res[[i]] <- 0L
}
}
else{
for (i in 1:gob$np) {
res[[i]] <- sort(gob$to[gob$from==i])
if(length(res[[i]]) == 0L) res[[i]] <- 0L
}
}
attr(res, "region.id") <- row.names
attr(res, "call") <- attr(gob, "call")
attr(res, "type") <- attr(gob, "type")
class(res) <- "nb"
res <- sym.attr.nb(res)
res
}
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