terra: union – R documentation

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union

Union SpatVector or SpatExtent objects

Description

Overlapping polygons (between, not within, objects) are intersected. Union for lines and points simply combines the two data sets; without any geometric intersections. This is equivalent to c. Attributes are joined. See c if you want to combine polygons without intersection.

If codex and y have a different geometry type, a SpatVectorCollection is returned.

If a single SpatVector is supplied, overlapping polygons are intersected. Original attributes are lost. New attributes allow for determining how many, and which, polygons overlapped.

SpatExtent: Objects are combined into their union; this is equivalent to +.

Usage

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

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

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

Arguments

`x`	SpatVector or SpatExtent
`y`	Same as `x` or missing

Value

SpatVector or SpatExtent

Examples

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

#SpatVector
v <- vect(system.file("ex/lux.shp", package="terra"))
v <- v[,3:4]
p <- vect(c("POLYGON ((5.8 49.8, 6 49.9, 6.15 49.8, 6 49.65, 5.8 49.8))", 
"POLYGON ((6.3 49.9, 6.2 49.7, 6.3 49.6, 6.5 49.8, 6.3 49.9))"), crs=crs(v))
values(p) <- data.frame(pid=1:2, value=expanse(p))
#u <- union(v, p)
#plot(u, "pid")

#b <- buffer(v, .015)
#u <- union(b)
#u$sum <- rowSums(as.data.frame(u))
#plot(u, "sum")

terra

Spatial Data Analysis

v1.2-10

GPL (>= 3)

Authors

Robert J. Hijmans [cre, aut] (<https://orcid.org/0000-0001-5872-2872>), Roger Bivand [ctb] (<https://orcid.org/0000-0003-2392-6140>), Karl Forner [ctb], Jeroen Ooms [ctb] (<https://orcid.org/0000-0002-4035-0289>), Edzer Pebesma [ctb] (<https://orcid.org/0000-0001-8049-7069>)

Initial release

2021-05-12