# R/maps.R In sf: Simple Features for R

#### Documented in st_as_sfc.mapst_as_sf.map

```NAmat2xyList <- function(xy) {
NAs <- unclass(attr(na.omit(xy), "na.action"))
if ((length(NAs) == 1L) && (NAs == nrow(xy))) {
xy <- xy[-nrow(xy)] # nocov
NAs <- NULL # nocov
}
# NA problem found by Edzer Pebesma, 24/8-06
diffNAs <- diff(NAs)
if (any(diffNAs == 1)) {
xy <- xy[-(NAs[which(diffNAs == 1)] + 1), ] # nocov
NAs <- unclass(attr(na.omit(xy), "na.action")) # nocov
}
nParts <- length(NAs) + 1L
# two NAs at end of file 070905 RSB
# no NAs at all RSB 080814
if (!is.null(NAs) && nrow(xy) == NAs[length(NAs)])
nParts <- nParts - 1
res <- vector(mode="list", length=nParts)
from <- integer(nParts)
to <- integer(nParts)
from <- 1
to[nParts] <- nrow(xy)
# two NAs at end of file 070905 RSB
# no NAs at all RSB 080814
if (!is.null(NAs) && nrow(xy) == NAs[length(NAs)])
to[nParts] <- to[nParts] - 1
if (nParts > 1) {
for (i in 2:nParts) {
to[(i-1)] <- NAs[(i-1)]-1
from[i] <- NAs[(i-1)]+1
}
}
for (i in seq_len(nParts))
res[[i]] <- xy[from[i]:to[i],, drop = FALSE]
res
}

map2pol = function(xyList, ID) {
# close rings:
xyList = lapply(xyList, ClosePol)
# group into MULTIPOLYGON:
uID = unique(ID)
ret = vector("list", length(uID))
for (g in seq_along(uID))
ret[[g]] = st_multipolygon(lapply(xyList[ uID[g] == ID ], function(x) list(x)))
st_sfc(ret)
}

map2lin = function(xyList, ID) {
# group into MULTILINESTRING:
uID = unique(ID)
ret = vector("list", length(uID))
for (g in seq_along(uID)) {
x = xyList[uID[g] == ID]
x = x[!sapply(x, is.null)]
ret[[g]] = st_multilinestring(x)
}
#		ret[[g]] = st_multilinestring(xyList[ uID[g] == ID ])
st_sfc(ret)
}

#' @export
#' @name st_as_sf
#' @param fill logical; the value for \code{fill} that was used in the call to \link[maps]{map}.
#' @param group logical; if \code{TRUE}, group id labels from \link[maps]{map} by their prefix before \code{:}
st_as_sf.map = function(x, ..., fill = TRUE, group = TRUE) {
ID = if (group)
vapply(strsplit(x\$names, ":"), function(y) y, "")
else
x\$names
xyList <- NAmat2xyList(cbind(x\$x, x\$y))
geom = if (fill)
map2pol(xyList, ID)
else
map2lin(xyList, ID)
st_sf(ID = unique(ID), geom = geom, crs = 4326)
}

#' @export
#' @name st_as_sfc
st_as_sfc.map = function(x, ...) {
st_geometry(st_as_sf(x, ...))
}
```

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sf documentation built on July 14, 2022, 5:08 p.m.