pintersect: Parallel set operations on polygons

In kevinrue/spatula: Utilities for Working with Spatial Data

Description

Perform set operations such as intersections and unions on two parallel SpatialPolygons objects. Requires installation of the rgeos package.

Usage

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

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

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

Arguments

x, y	SpatialPolygons objects to be processed in parallel. The shorter object is recycled to the same length as the larger object.

Details

These functions iterate through x and y simultaneously to take the intersection, union, etc. of the corresponding polygons in the two objects.

If the intersection is empty, a polygon is returned with zero area and all vertices at the origin. This is necessary because, unfortunately, the Polygons constructor does not support empty lists.

Lines or points formed by intersections are currently ignored.

Value

A SpatialPolygons object representing the intersection, union or difference of the polygons.

Author(s)

Aaron Lun

Examples

poly <- makeSpatialPolygons(
    rbind(c(0,0), c(0.5, 0), c(0.5, 0.5), c(0, 0.5)),
    rbind(c(1,1), c(0.5, 1), c(0.5, 0.5), c(1, 0.5)),
    rbind(c(0.5,0), c(1, 0), c(1, 0.5), c(0.5, 0.5)),
    rbind(c(0,1), c(0.5, 1), c(0.5, 0.5), c(0, 0.5))
)
plot(poly)

other.poly <- makeSpatialPolygons(
    rbind(c(0.1,0.1), c(0.7, 0.1), c(0.7, 0.7), c(0.1, 0.7))
)

intersected <- pintersect(poly, other.poly)
plot(intersected[1], xlim=c(0, 1), ylim=c(0, 1))

unioned <- punion(poly, other.poly)
plot(unioned[1], xlim=c(0, 1), ylim=c(0, 1))

diffed <- psetdiff(poly, other.poly)
plot(diffed[1], xlim=c(0, 1), ylim=c(0, 1))

kevinrue/spatula documentation built on May 9, 2020, 8:42 a.m.