R: Create a Line Segment Pattern

psp {spatstat.geom} | R Documentation

## 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.

### 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 ith 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.

### Value

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

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz.

### See Also

`psp.object`, `as.psp`, `owin.object`, `owin`, `as.owin`.

Function for extracting information from a segment pattern: `marks.psp`, `summary.psp`, `midpoints.psp`, `lengths_psp` `angles.psp`, `endpoints.psp`

Convert line segments to infinite lines: `extrapolate.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)

[Package spatstat.geom version 2.2-0 Index]