new-generics | R Documentation |

Some generic functions and methods for polygon objects

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

`x,object` |
A polygon object |

`y` |
A polygon object |

`...` |
Other arguments passed to methods |

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.

- 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.

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

`"gpc.poly"`

class documentation.

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

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