new-generics: Generics/Methods for polygon objects

Description

Some generic functions and methods for polygon objects

Usage

append.poly(x, y)
area.poly(object, ...)
get.pts(object)
get.bbox(x)
scale.poly(x, ...)
tristrip(x)
triangulate(x)

Arguments

x,object

A polygon object

...

Other arguments passed to methods

Methods

append.poly: signature(x = "gpc.poly", y = "gpc.poly"): Combine all contours of two "gpc.poly" objects and return the combined polygon as a "gpc.poly" object.
area.poly: signature(object = "gpc.poly"): Compute and return the sum of the areas of all contours in a "gpc.poly" object.
scale.poly: signature(x = "gpc.poly"): Scale (divide) the x and y coordinates of a "gpc.poly" object by the amount xscale and yscale, respectively. Return a scaled "gpc.poly" object.
get.pts: signature(object = "gpc.poly"): Return the list of x and y coordinates of the vertices of a "gpc.poly" object.
get.bbox: signature(x = "gpc.poly"): Return the bounding box for a "gpc.poly" object.
tristrip: signature(x = "gpc.poly"): Return a tristrip list for a "gpc.poly" object.
triangulate: signature(x = "gpc.poly"): Return a matrix of vertices of a triangulation of a "gpc.poly" object.

Details

The result of tristrip(x) is a list of two-column matrices. Each matrix is a tristrip, i.e. the rows are vertices of triangles, with each overlapping triple of rows corresponding to a separate triangle.

The result of triangulate(x) is a single two-column matrix. The rows are vertices of triangles, taken in non-overlapping triples.

Examples

Run this code

holepoly <- read.polyfile(system.file("poly-ex-gpc/hole-poly.txt",
 package ="rgeos"), nohole = FALSE)
area.poly(holepoly)
stopifnot(area.poly(holepoly) == 8)