R: Determines area of a polygon by triangle method.

polyarea {geometry} | R Documentation

## Determines area of a polygon by triangle method.

### Description

Determines area of a polygon by triangle method. The variables `x` and `y` define the vertex pairs, and must therefore have the same shape. They can be either vectors or arrays. If they are arrays then the columns of `x` and `y` are treated separately and an area returned for each.

### Usage

    polyarea(x, y, d = 1)

### Arguments

`x` | X coordinates of verticies.
`y` | Y coordinates of verticies.
`d` | Dimension of array to work along.

### Details

If the optional `dim` argument is given, then `polyarea` works along this dimension of the arrays `x` and `y`.

### Value

Area(s) of polygon(s).

### Author(s)

David Sterratt based on the octave sources by David M. Doolin

### Examples

    x <- c(1, 1, 3, 3, 1)
    y <- c(1, 3, 3, 1, 1)
    polyarea(x, y)
    polyarea(cbind(x, x), cbind(y, y)) ##  c(4, 4)
    polyarea(cbind(x, x), cbind(y,y), 1) ##  c(4, 4)
    polyarea(rbind(x, x), rbind(y,y), 2) ##  c(4, 4)

[Package geometry version 0.3-6 Index]