union: Union Extent or SpatialPolygons* objects

In raster: Geographic Data Analysis and Modeling

Description

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.

Usage

## 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

Value

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
if (require(rgdal) & require(rgeos)) {
	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)
}

Example output

Loading required package: sp
class       : Extent 
xmin        : -10 
xmax        : 20 
ymin        : -40 
ymax        : 20 
Loading required package: rgdal
Loading required package: rgeos
Warning messages:
1: In library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called 'rgdal'
2: In library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called 'rgeos'

raster documentation built on Jan. 5, 2021, 3:01 a.m.