topo-unary-gEnvelope: Envelope of Geometry

In rgeos: Interface to Geometry Engine - Open Source ('GEOS')

Envelope of Geometry

Description

Function calculates the rectangular bounding box for the given geometry

Usage

gEnvelope(spgeom, byid=FALSE, id = NULL)

Arguments

spgeom	sp object as defined in package sp
byid	Logical determining if the function should be applied across subgeometries (TRUE) or the entire object (FALSE)
id	Character vector defining id labels for the resulting geometries, if unspecified returned geometries will be labeled based on their parent geometries' labels.

Details

Returns the rectangular bounding box as a SpatialPolygons object. If spgeom is a degenerate case (horizontal/vertical line, single point) then the function may return an object with lower dimension (SpatialLines or SpatialPoints) or an invalid polygon.

Author(s)

Roger Bivand & Colin Rundel

See Also

gBoundary gCentroid gConvexHull gPointOnSurface

Examples

x = readWKT(paste("POLYGON((0 40,10 50,0 60,40 60,40 100,50 90,60 100,60",
 "60,100 60,90 50,100 40,60 40,60 0,50 10,40 0,40 40,0 40))"))
env = gEnvelope(x)

plot(x,col='blue',border='blue')
plot(env,add=TRUE)

#Degenerate Cases
gEnvelope(readWKT("POINT(1 1)")) #returns SpatialPoints
gEnvelope(readWKT("LINESTRING(1 1,1 2)")) #invalid polygon
gEnvelope(readWKT("LINESTRING(1 1,2 1)")) #invalid polygon

rgeos documentation built on July 26, 2023, 5:42 p.m.