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

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.

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.

Author(s)

Roger D. Peng; GPC Library by Alan Murta; tristrip additions by Duncan Murdoch

See Also

"gpc.poly" class documentation.

Examples

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