Geometry Relationships - Intersects and Disjoint
Function for testing if the geometries have at least one point in common or no points in common
gIntersects(spgeom1, spgeom2 = NULL, byid = FALSE, prepared=TRUE, returnDense=TRUE, checkValidity=FALSE) gDisjoint(spgeom1, spgeom2 = NULL, byid = FALSE, returnDense=TRUE, checkValidity=FALSE)
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. |
returnDense |
default TRUE, if false returns a list of the length of spgeom1 of integer vectors listing the |
checkValidity |
default FALSE; error meesages from GEOS do not say clearly which object fails if a topology exception is encountered. If this argument is TRUE, |
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.
Both return a conforming logical matrix if byid = TRUE.
Error messages from GEOS, in particular topology exceptions, report 0-based object order, so geom 0 is spgeom1, and geom 1 is spgeom2.
Roger Bivand & Colin Rundel
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)))
# Michael Chirico bug report and fix 2019-08-16
SP1 = SpatialPoints(
cbind(c(.25, .75), c(.75, .25)) )
SP2 = SpatialPolygons(list(
Polygons(list(Polygon(cbind(c(0, 0, 1, 1), c(0, 1, 1, 0)))), ID = 'a'),
Polygons(list(Polygon(cbind(c(1, 1, 2, 2), c(1, 2, 2, 1)))), ID = 'b')
))
gIntersects(SP1, SP2, byid = c(TRUE, FALSE))
gIntersects(SP1, SP2, byid = c(TRUE, TRUE))
gIntersects(SP1, SP2, byid = c(FALSE, TRUE))
gIntersects(SP1, SP2, byid = c(FALSE, FALSE))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.