# new-generics {rgeos}

Generics/Methods for polygon objects
Package:
rgeos
Version:
0.3-19

### 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

### 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 = &nbsp;&nbsp;&nbsp;&nbsp;"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.

`"gpc.poly"` class documentation.

### Examples

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

### Author(s)

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

Documentation reproduced from package rgeos, version 0.3-19. License: GPL (>= 2)