gIntersects {rgeos}R Documentation

Geometry Relationships - Intersects and Disjoint

Description

Function for testing if the geometries have at least one point in common or no points in common

Usage

	gIntersects(spgeom1, spgeom2 = NULL, byid = FALSE, prepared=TRUE)
	gDisjoint(spgeom1, spgeom2 = NULL, byid = FALSE)

Arguments

spgeom1, spgeom2

sp objects as defined in package sp. If spgeom2 is NULL then spgeom1 is compared to itself.

byid

Logical vector determining if the function should be applied across ids (TRUE) or the entire object (FALSE) for spgeom1 and spgeom2

prepared

Logical determining if prepared geometry (spatially indexed) version of the GEOS function should be used. In general prepared geometries should be faster than the alternative.

Value

gIntersects returns TRUE if spgeom1 and spgeom2 have at least one point in common.

gDisjoint returns TRUE if spgeom1 and spgeom2 have no points in common.

Author(s)

Roger Bivand & Colin Rundel

See Also

gContains gContainsProperly gCovers gCoveredBy gCrosses gEquals gEqualsExact gOverlaps gRelate gTouches gWithin

Examples

	p1 = readWKT("POLYGON((0 0,1 0,1 1,0 1,0 0))")
	p2 = readWKT("POLYGON((0.5 1,0 2,1 2,0.5 1))")
	p3 = readWKT("POLYGON((0.5 0.5,0 1.5,1 1.5,0.5 0.5))")

	l1 = readWKT("LINESTRING(0 3,1 1,2 2,3 0)")
	l2 = readWKT("LINESTRING(1 3.5,3 3,2 1)")
	l3 = readWKT("LINESTRING(-0.1 0,-0.1 1.1,1 1.1)")
	
	pt1 = readWKT("MULTIPOINT(1 1,3 0,2 1)")
	pt2 = readWKT("MULTIPOINT(0 3,3 0,2 1)")
	pt3 = readWKT("MULTIPOINT(-0.2 0,1 -0.2,1.2 1,0 1.2)")

	
	par(mfrow=c(3,2))
	plot(p1,col='blue',border='blue',ylim=c(0,2.5));plot(p2,col='black',add=TRUE,pch=16)
	title(paste("Intersects:",gIntersects(p1,p2),
				"\nDisjoint:",gDisjoint(p1,p2)))
	
	plot(p1,col='blue',border='blue',ylim=c(0,2.5));plot(p3,col='black',add=TRUE,pch=16)
	title(paste("Intersects:",gIntersects(p1,p3),
				"\nDisjoint:",gDisjoint(p1,p3)))
				
	plot(l1,col='blue');plot(pt1,add=TRUE,pch=16)
	title(paste("Intersects:",gIntersects(l1,pt1),
				"\nDisjoint:",gDisjoint(l1,pt1)))
	
	plot(l1,col='blue');plot(pt2,add=TRUE,pch=16)
	title(paste("Intersects:",gIntersects(l1,pt2),
				"\nDisjoint:",gDisjoint(l1,pt2)))
	
	plot(p1,col='blue',border='blue',xlim=c(-0.5,2),ylim=c(0,2.5));plot(l3,lwd=2,col='black',add=TRUE)
	title(paste("Intersects:",gIntersects(p1,l3),
				"\nDisjoint:",gDisjoint(p1,l3)))
	
	plot(p1,col='blue',border='blue',xlim=c(-0.5,2),ylim=c(-0.5,2));plot(pt3,pch=16,col='black',add=TRUE)
	title(paste("Intersects:",gIntersects(p1,pt3),
				"\nDisjoint:",gDisjoint(p1,pt3)))

[Package rgeos version 0.2-2 Index]