Endpoints of Line Segment Pattern

Description

Extracts the endpoints of each line segment in a line segment pattern.

Usage

  endpoints.psp(x, which="both")

Arguments

Details

This function extracts one endpoint, or both endpoints, from each of the line segments in x, and returns these points as a point pattern object.

The argument which determines which endpoint or endpoints of each line segment should be returned:

which="both"

(the default): both endpoints of each line segment are returned. The result is a point pattern with twice as many points as there are line segments in x.

which="first"

select the first endpoint of each line segment (returns the points with coordinates x$ends$x0, x$ends$y0).

which="second"

select the second endpoint of each line segment (returns the points with coordinates x$ends$x1, x$ends$y1).

which="left"

select the left-most endpoint (the endpoint with the smaller x coordinate) of each line segment.

which="right"

select the right-most endpoint (the endpoint with the greater x coordinate) of each line segment.

which="lower"

select the lower endpoint (the endpoint with the smaller y coordinate) of each line segment.

which="upper"

select the upper endpoint (the endpoint with the greater y coordinate) of each line segment.

The result is a point pattern. It also has an attribute "id" which is an integer vector identifying the segment which contributed each point.

Value

Point pattern (object of class "ppp").

Author(s)

Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf

See Also

psp.object, ppp.object, midpoints.psp

Examples

  a <- psp(runif(10), runif(10), runif(10), runif(10), window=owin())
  plot(a)
  b <- endpoints.psp(a, "left")
  plot(b, add=TRUE)