Geometry Relationships - Intersection Matrix Pattern (DE-9IM)

Description

Determines the relationships between two geometries by comparing the intersection of Interior, Boundary and Exterior of both geometries to each other. The results are summarized by the Dimensionally Extended 9-Intersection Matrix or DE-9IM.

Usage

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	gRelate(spgeom1, spgeom2 = NULL, pattern = NULL, byid = FALSE,
 checkValidity=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

pattern

Character string containing intersection matrix pattern to match against DE-9IM for given geometries. Wild card * or * characters allowed.

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, gIsValid is run on each in turn in an environment in which object names are available. If objects are invalid, this is reported and those affected are named

Details

Each geometry is decomposed into an interior, a boundary, and an exterior region, all the resulting geometries are then tested by intersection against one another resulting in 9 total comparisons. These comparisons are summarized by the dimensions of the intersection region, as such intersection at point(s) is labeled 0, at linestring(s) is labeled 1, at polygons(s) is labeled 2, and if they do not intersect labeled F.

If a pattern is specified then limited matching with wildcards is possible, * matches any character whereas T matches any non-F character.

See references for additional details.

Value

By default returns a 9 character string that represents the DE-9IM.

If pattern returns TRUE if the pattern matches the DE-9IM.

Note

Error messages from GEOS, in particular topology exceptions, report 0-based object order, so geom 0 is spgeom1, and geom 1 is spgeom2.

Author(s)

Roger Bivand & Colin Rundel

References

Documentation of Intersection Matrix Patterns: http://docs.geotools.org/stable/userguide/library/jts/dim9.html

See Also

gContains gContainsProperly gCovers gCoveredBy gCrosses gDisjoint gEquals gEqualsExact gIntersects gOverlaps gTouches gWithin

Examples

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	x = readWKT("POLYGON((1 0,0 1,1 2,2 1,1 0))")
	x.inter = x
	x.bound = gBoundary(x)
	
	y = readWKT("POLYGON((2 0,1 1,2 2,3 1,2 0))")
	y.inter = y
	y.bound = gBoundary(y)
	
	
	xy.inter = gIntersection(x,y)
	xy.inter.bound = gBoundary(xy.inter)
	
	xy.union = gUnion(x,y)
	bbox = gBuffer(gEnvelope(xy.union),width=0.5,joinStyle='mitre',mitreLimit=3)

	x.exter = gDifference(bbox,x)
	y.exter = gDifference(bbox,y)

	# geometry decomposition
	par(mfrow=c(2,3))
	plot(bbox,border='grey');plot(x,col="black",add=TRUE);title("Interior",ylab = "Polygon X")
	plot(bbox,border='grey');plot(x.bound,col="black",add=TRUE);title("Boundary")
	plot(bbox,border='grey');plot(x.exter,col="black",pbg='white',add=TRUE);title("Exterior")
	plot(bbox,border='grey');plot(y,col="black",add=TRUE);title(ylab = "Polygon Y")
	plot(bbox,border='grey');plot(y.bound,col="black",add=TRUE)
	plot(bbox,border='grey');plot(y.exter,col="black",pbg='white',add=TRUE)
	
	
	
	defaultplot = function() {
		plot(bbox,border='grey')
		plot(x,add=TRUE,col='red1',border="red3")
		plot(y,add=TRUE,col='blue1',border="blue3")		
		plot(xy.inter,add=TRUE,col='orange1',border="orange3")
	}
	
	# Dimensionally Extended 9-Intersection Matrix
	pat = gRelate(x,y)
	patchars = strsplit(pat,"")[[1]]
	
	par(mfrow=c(3,3))
	defaultplot(); plot(gIntersection(x.inter,y.inter),add=TRUE,col='black')
	title(paste("dim:",patchars[1]))
	defaultplot(); plot(gIntersection(x.bound,y.inter),add=TRUE,col='black',lwd=2)
	title(paste("dim:",patchars[2]))
	defaultplot(); plot(gIntersection(x.exter,y.inter),add=TRUE,col='black')
	title(paste("dim:",patchars[3]))
	
	defaultplot(); plot(gIntersection(x.inter,y.bound),add=TRUE,col='black',lwd=2)
	title(paste("dim:",patchars[4]))
	defaultplot(); plot(gIntersection(x.bound,y.bound),add=TRUE,col='black',pch=16)
	title(paste("dim:",patchars[5]))
	defaultplot(); plot(gIntersection(x.exter,y.bound),add=TRUE,col='black',lwd=2)
	title(paste("dim:",patchars[6]))
	
	defaultplot(); plot(gIntersection(x.inter,y.exter),add=TRUE,col='black')
	title(paste("dim:",patchars[7]))
	defaultplot(); plot(gIntersection(x.bound,y.exter),add=TRUE,col='black',lwd=2)
	title(paste("dim:",patchars[8]))
	defaultplot(); plot(gIntersection(x.exter,y.exter),add=TRUE,col='black')
	title(paste("dim:",patchars[9]))
	

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