m

man/convhull.Rd

@@ -18,7 +18,7 @@ Convex, concave, rectangular and circular hulls
 \description{
 Compute hulls around SpatVector geometries. This can be the convex hull, the minimal bounding rotated rectangle, the minimal bounding circle, or a concave hull. The concaveness of the concave hull can be specified in different ways.
 
-The old methods \code{convHull}, \code{minRect} and \code{minCircle} are depracated and will be removed in a future version.
+The old methods \code{convHull}, \code{minRect} and \code{minCircle} are deprecated and will be removed in a future version.
 }
 
 \usage{
@@ -27,17 +27,26 @@ The old methods \code{convHull}, \code{minRect} and \code{minCircle} are depraca
 
 \arguments{
   \item{x}{SpatVector}
-  \item{type}{character. One of "convex", "rectangle", "circle", "concave_ratio", "concave_length", "concave_polygons"}
+  \item{type}{character. One of "convex", "rectangle", "circle", "concave_ratio", "concave_length"}
   \item{by}{character (variable name), to get a new geometry for groups of input geometries}
   \item{param}{numeric between 0 and 1. For the "concave_*" types only. For \code{type="concave_ratio"} this is The edge length ratio value, between 0 and 1. For \code{type="concave_length"} this the maximum edge length (a value > 0). For \code{type="concave_polygons"} thism specifies the maximum Edge Length as a fraction of the difference between the longest and shortest edge lengths between the polygons. This normalizes the maximum edge length to be scale-free. A value of 1 produces the convex hull; a value of 0 produces the original polygons}
-  \item{allowHoles}{logical. May the polygonal output contain holes? For the "concave_* types only}
-  \item{tight}{logical. Should the hull follow the outer boundaries of the input polygons? For the "concave_* types only}
+  \item{allowHoles}{logical. May the output polygons contain holes? For "concave_*" methods only}
+  \item{tight}{logical. Should the hull follow the outer boundaries of the input polygons? For "concave_length" with polygon geometry only}
 }
 
 \value{
 SpatVector
 }
 
+
+\details{
+A concave hull is a polygon which contains all the points of the input. It can be a better representation of the input data (typically points) than the convex hull. There are many possible convex hulls with different degrees of concaveness. These can be created with argument \code{param}.
+
+The hull is constructed by removing the longest outer edges of the Delaunay Triangulation of the space between the polygons, until the target criterion \code{param} is reached. If \code{type="concave_ratio"}, \code{param} expresses is the ratio between the lengths of the longest and shortest edges. 1 produces the convex hull; 0 produces a hull with maximum concaveness. If \code{type="concave_length"}, \code{param} specifies the maximm edge length. A large value produces the convex hull, 0 produces the hull of maximum concaveness.
+}
+
+
+
 \examples{
 p <- vect(system.file("ex/lux.shp", package="terra"))
 h <- hull(p)

src/geos_methods.cpp

@@ -992,6 +992,12 @@ SpatVector SpatVector::hull(std::string htype, std::string by, double param, boo
 		return out;
 	}
 
+	std::vector<std::string> methods = {"convex", "rectangle", "circle", "concave_ratio", "concave_length"};
+	if (std::find(methods.begin(), methods.end(), htype) == methods.end()) {
+		out.setError("unknown hull type");
+		return out;
+	}
+
 	if (!by.empty()) {
 		SpatVector tmp = aggregate(by, false);
 		if (tmp.hasError()) {
@@ -1017,21 +1023,16 @@ SpatVector SpatVector::hull(std::string htype, std::string by, double param, boo
 
 	out.reserve(size());
 
-
-	if (htype != "convex") {
-		#ifndef GEOS361
-		out.setError("GEOS 3.6.1 required for rotated rectangle");
-		return out;
-		#endif
-		if (is_lonlat()) {
-			if ((extent.ymin > -85) && (extent.ymax < 85)) {
-				SpatVector tmp = project("+proj=merc", false);
-				tmp = tmp.hull(htype, "");
-				tmp = tmp.project(srs.wkt, false);
-				return tmp;
-			}
+/*
+	if (is_lonlat()) {
+		if ((extent.ymin > -85) && (extent.ymax < 85)) {
+			SpatVector tmp = project("+proj=merc", false);
+			tmp = tmp.hull(htype, "");
+			tmp = tmp.project(srs.wkt, false);
+			return tmp;
 		}
 	}
+*/
 
 	SpatVector a = aggregate(false);
 
@@ -1066,9 +1067,11 @@ SpatVector SpatVector::hull(std::string htype, std::string by, double param, boo
 		if (htype == "concave_ratio") {
 			h = GEOSConcaveHull_r(hGEOSCtxt, g[0].get(), param, allowHoles);
 		} else if (htype == "concave_length") {
-			h = GEOSConcaveHullByLength_r(hGEOSCtxt, g[0].get(), param, allowHoles);
-		} else if (htype == "concave_polygons") {
-			h = GEOSConcaveHullOfPolygons_r(hGEOSCtxt, g[0].get(), param, tight, allowHoles);
+			if (type() == "polygons") {
+				h = GEOSConcaveHullOfPolygons_r(hGEOSCtxt, g[0].get(), param, tight, allowHoles);
+			} else {
+				h = GEOSConcaveHullByLength_r(hGEOSCtxt, g[0].get(), param, allowHoles);
+			}
 		} else {
 			geos_finish(hGEOSCtxt);
 			out.setError("unknown hull type");