spatstat (version 1.31-3)

psp: Create a Line Segment Pattern

Description

Creates an object of class "psp" representing a line segment pattern in the two-dimensional plane.

Usage

psp(x0,y0, x1, y1, window, marks=NULL,
        check=spatstat.options("checksegments"))

Arguments

x0

Vector of $x$ coordinates of first endpoint of each segment

y0

Vector of $y$ coordinates of first endpoint of each segment

x1

Vector of $x$ coordinates of second endpoint of each segment

y1

Vector of $y$ coordinates of second endpoint of each segment

window

window of observation, an object of class "owin"

marks

(optional) vector or data frame of mark values

check

Logical value indicating whether to check that the line segments lie inside the window.

Value

• An object of class "psp" describing a line segment pattern in the two-dimensional plane (see psp.object).

Details

In the spatstat library, a spatial pattern of line segments is described by an object of class "psp". This function creates such objects.

The vectors x0, y0, x1 and y1 must be numeric vectors of equal length. They are interpreted as the cartesian coordinates of the endpoints of the line segments.

A line segment pattern is assumed to have been observed within a specific region of the plane called the observation window. An object of class "psp" representing a point pattern contains information specifying the observation window. This window must always be specified when creating a point pattern dataset; there is intentionally no default action of ``guessing'' the window dimensions from the data points alone.

The argument window must be an object of class "owin". It is a full description of the window geometry, and could have been obtained from owin or as.owin, or by just extracting the observation window of another dataset, or by manipulating such windows. See owin or the Examples below.

The optional argument marks is given if the line segment pattern is marked, i.e. if each line segment carries additional information. For example, line segments which are classified into two or more different types, or colours, may be regarded as having a mark which identifies which colour they are.

The object marks must be a vector of the same length as x0, or a data frame with number of rows equal to the length of x0. The interpretation is that marks[i] or marks[i,] is the mark attached to the $i$th line segment. If the marks are real numbers then marks should be a numeric vector, while if the marks takes only a finite number of possible values (e.g. colours or types) then marks should be a factor.

See psp.object for a description of the class "psp".

Users would normally invoke psp to create a line segment pattern, and the function as.psp to convert data in another format into a line segment pattern.

See Also

psp.object, as.psp, owin.object, owin, as.owin, marks.psp

Examples

X <- psp(runif(10), runif(10), runif(10), runif(10), window=owin())
  m <- data.frame(A=1:10, B=letters[1:10])
  X <- psp(runif(10), runif(10), runif(10), runif(10), window=owin(), marks=m)