polygon: Polygon Functions

In TobieSurette/gulf.graphics: Southern Gulf Graphics Functions

Polygon Functions

Description

Set of functions to create, manipulate and query polygon objects.

Usage

polygon(x, ...)

## Default S3 method:
polygon(x, ...)

as.polygon(x, y = NULL, hole = NULL, ...)

## S3 method for class 'polygon'
plot(p, labels = FALSE, as.lines = FALSE, ...)

in.polygon(p, x, y, ...)

which.polygon(p, x, y, as.list = FALSE)

## S3 method for class 'polygon'
as.data.frame(x)

is.polygon(p)

Arguments

x	May be either a ‘polygon’ object, a list containing polygon vertex definitions (with ‘x’ and ‘y’ coordinates or longitude and latitude) or a numeric vector of horizontal polygon vertex coordinates.
y	A numeric vector of vertical polygon vertex coordinates.
hole	A logical vector specifying whether component polygons are to be treated as holes. The length of the vector may be either the same as numeric ‘x’ and ‘y’ or its length may be that of the number of component polygons of the object. Polygons labelled as holes have negative areas.
p	List vector of polygon object definitions. Each element in the list corresponds to a single polygon object. They contain two fields, x and y, defining the vertices of each polygon.

Value

logical value TRUE is returned when a point (x, y) lies within and FALSE if it lies outside each polygon.

Functions

polygon, as.polygon

Creates or converts to a ‘polygon’ object.

plot.polygon

Graphically display a polygon object.

in.polygon

Determine whether a coordinate point lies within a polygon. A logical (n by k) matrix is returned where n is the number of component polygons in p and k is the length of the x and y vectors.

which.polygon

Returns the indices specifying to which polygon(s) in a list a point belongs.

area.polygon

Calculates the area of a polygon.

as.data.frame.polygon

Convert polygon object to data frame.

bbox.polygon

Determine bounding box for a polygon object.

draw.polygon

Draw a polygon on a plot.

is.polygon

Checks whether object is a ‘polygon’ object.

See Also

point.in.polygon

Examples

# Define set of polygon vertices:
x <- c(0, 0, 0.5, 1, 1, 0)
y <- c(0, 1, 0.5, 1, 0, 0)
p <- as.polygon(x, y)
plot(p) # Plot polygon.
area(p) # Calculate area of polygon.

# Generate set of random points:
x <- runif(1000)*2-0.5
y <- runif(1000)*2-0.5

# Plot points:
plot(c(-0.5, 1.5), c(-0.5, 1.5), type = "n")
index <- in.polygon(p, x, y)
points(x[index], y[index], pch = 21, bg = "red")
points(x[!index], y[!index], pch = 21, bg = "blue")

TobieSurette/gulf.graphics documentation built on Feb. 10, 2024, 10:58 p.m.