union function

Union Extent or SpatialPolygons* objects

Extent objects: Objects are combined into their union. See crop and extend to union a Raster object with an Extent object.

Two SpatialPolygons* objects. Overlapping polygons (between layers, not within layers) are intersected, other spatial objects are appended. Tabular attributes are joined. See bind if you want to combine polygons without intersection.

Single SpatialPolygons* object. Overlapping polygons are intersected. Original attributes are lost. New attributes allow for determining how many, and which, polygons overlapped.

Union for SpatialLines and SpatialPoints simply combines the two data sets; without any geometric intersections. This is equivalent to bind. methods

## S4 method for signature 'Extent,Extent'
union(x, y)

## S4 method for signature 'SpatialPolygons,SpatialPolygons'
union(x, y)

## S4 method for signature 'SpatialPolygons,missing'
union(x, y)

## S4 method for signature 'SpatialLines,SpatialLines'
union(x, y)

## S4 method for signature 'SpatialPoints,SpatialPoints'
union(x, y)

Arguments

• x: Extent or SpatialPolygons* object
• y: Same as x or missing

Returns

Extent or SpatialPolygons object

See Also

intersect, extent, setExtent

merge for merging a data.frame with attributes of Spatial objects and +,SpatialPolygons,SpatialPolygons-method for an algebraic notation

Examples

e1 <- extent(-10, 10, -20, 20)
e2 <- extent(0, 20, -40, 5)
union(e1, e2)

#SpatialPolygons
p <- shapefile(system.file("external/lux.shp", package="raster"))
p0 <- aggregate(p)
b <- as(extent(6, 6.4, 49.75, 50), 'SpatialPolygons')
crs(b) <- crs(p)
u <- union(p0, b)
plot(u, col=2:4)