address #733

NEWS.md

@@ -1,10 +1,10 @@
 # version 0.6-9
 
-* 
+* `st_sfc2xy()` passes on `...` to `st_as_stars()`; #733 
 
 # version 0.6-8
 
-* address difftime issue new in R-devel rev 87670
+* address `/.difftime` issue new in R-devel rev 87670
 
 * `c.stars()` is more strict when combining time sequences; #703
 

R/rasterize.R

@@ -247,22 +247,3 @@ st_as_stars.data.frame = function(.x, ..., dims = coords, xy, y_decreasing = TRU
 	)
 	st_stars(l, d)
 }
-
-#' replace POINT simple feature geometry list with an x y raster
-#' @param x object of class \code{stars}, or of class \code{sf}
-#' @param ... passed on to \link{as.data.frame.stars}
-#' @return object of class \code{stars} with a POINT list replaced by x and y raster dimensions. This only works when the points are distributed over a regular or rectilinear grid.
-#' @export
-st_sfc2xy = function(x, ...) {
-	if (inherits(x, "sf"))
-		x = st_as_stars(x)
-	i = which_sfc(x)
-	d = st_dimensions(x)
-	if (!inherits(d[[i]]$values, "sfc_POINT"))
-		stop("point geometries expected")
-	cc = st_coordinates(d[[i]]$values)
-	df = as.data.frame(x)
-	df$geometry = NULL
-	s = st_as_stars(cbind(cc, df))
-	st_set_crs(s, st_crs(d))
-}

R/sf.R

@@ -27,13 +27,13 @@ st_as_sfc.stars = function(x, ..., as_points, which = seq_len(prod(dim(x)[1:2]))
 		sfc
 }
 
-
-#' replace x y raster dimensions with simple feature geometry list (points, or polygons = rasterize)
+#' replace x y raster dimensions with simple feature geometry list (points, or polygons = rasterize) and vice versa
 #' @param x object of class \code{stars}
 #' @param as_points logical; if \code{TRUE}, generate points at cell centers, else generate polygons
 #' @param ... arguments passed on to \code{st_as_sfc}
 #' @param na.rm logical; omit (remove) cells which are entirely missing valued (across other dimensions)?
-#' @return object of class \code{stars} with x and y raster dimensions replaced by a single sfc geometry list column containing either points, or polygons. Adjacent cells with identical values are not merged; see \code{st_rasterize} for this.
+#' @details `st_xy2sfc` replaces x y raster dimensions with simple feature geometry list (points, or polygons = rasterize)
+#' @return `st_xy2sfc` returns an object of class \code{stars} with x and y raster dimensions replaced by a single sfc geometry list column containing either points, or polygons. Adjacent cells with identical values are not merged; see \code{st_rasterize} for this.
 #' @export
 st_xy2sfc = function(x, as_points, ..., na.rm = TRUE) {
 
@@ -86,6 +86,37 @@ st_xy2sfc = function(x, as_points, ..., na.rm = TRUE) {
 	st_stars(x, dimensions = d)
 }
 
+#' @details `st_sfc2xy` replaces POINT simple feature geometry list with an x y raster
+#' @param x object of class \code{stars}, or of class \code{sf}
+#' @param ... passed on to \link{st_as_stars.data.frame}
+#' @return `st_sfc2xy` returns an object of class \code{stars} with a POINT list replaced by X and Y raster dimensions. This only works when the points are distributed over a regular or rectilinear grid.
+#' @export
+#' @name st_xy2sfc
+#' @examples
+#' (reduced_nc = read_ncdf(system.file("nc/reduced.nc", package = "stars")))
+#' (x = stars::st_xy2sfc(reduced_nc, as_points = TRUE, na.rm = FALSE))
+#' # roundtrip:
+#' st_sfc2xy(x, dims=c("X", "Y","zlev","time"))
+st_sfc2xy = function(x, ...) {
+	if (inherits(x, "sf"))
+		x = st_as_stars(x)
+	i = which_sfc(x)
+	if (length(i) == 0)
+		stop("x does not contain a geometry dimension")
+	if (length(i) > 1) {
+		stop("using first geometry dimension only")
+		i = i[1]
+	}
+	d = st_dimensions(x)
+	if (!inherits(d[[i]]$values, "sfc_POINT"))
+		stop("point geometries expected")
+	cc = st_coordinates(d[[i]]$values)
+	df = as.data.frame(x)
+	df$geometry = NULL
+	s = st_as_stars(cbind(cc, df), ...)
+	st_set_crs(s, st_crs(d))
+}
+
 #' @export
 st_as_sf.dimensions = function(x, ...) {
 	ix = which_sfc(x)[1]