gpclib (version 1.5-6)

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

y

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.

See Also

"gpc.poly" class documentation.

Examples

# NOT RUN {
holepoly <- read.polyfile(system.file("poly-ex/hole-poly.txt", package =
"gpclib"), nohole = FALSE)
area.poly(holepoly)
stopifnot(area.poly(holepoly) == 8)
# }