R: Sector K-function

Ksector {spatstat.core} | R Documentation

## Sector K-function

### Description

A directional counterpart of Ripley's K function, in which pairs of points are counted only when the vector joining the pair happens to lie in a particular range of angles.

### Usage

    Ksector(X, begin = 0, end = 360, ...,
            units = c("degrees", "radians"),
            r = NULL, breaks = NULL,
            correction = c("border", "isotropic", "Ripley", "translate"),
            domain=NULL, ratio = FALSE, verbose=TRUE)

### Arguments

`X` | The observed point pattern, from which an estimate of K(r) will be computed. An object of class `"ppp"`, or data in any format acceptable to `as.ppp()`.
`begin,end` | Numeric values giving the range of angles inside which points will be counted. Angles are measured in degrees (if `units="degrees"`, the default) or radians (if `units="radians"`) anti-clockwise from the positive x-axis.
`...` | Ignored.
`units` | Units in which the angles `begin` and `end` are expressed.
`r` | Optional. Vector of values for the argument r at which K(r) should be evaluated. Users are advised not to specify this argument; there is a sensible default.
`breaks` | This argument is for internal use only.
`correction` | Optional. A character vector containing any selection of the options `"none"`, `"border"`, `"bord.modif"`, `"isotropic"`, `"Ripley"`, `"translate"`, `"translation"`, `"none"`, `"good"` or `"best"`. It specifies the edge correction(s) to be applied. Alternatively `correction="all"` selects all options.
`domain` | Optional window. The first point x[i] of each pair of points will be constrained to lie in `domain`.
`ratio` | Logical. If `TRUE`, the numerator and denominator of each edge-corrected estimate will also be saved, for use in analysing replicated point patterns.
`verbose` | Logical value indicating whether to print progress reports and warnings.

### Details

This is a directional counterpart of Ripley's K function (see `Kest`) in which, instead of counting all pairs of points within a specified distance r, we count only the pairs x[i], x[j] for which the vector x[j] - x[i] falls in a particular range of angles.

This can be used to evaluate evidence for anisotropy in the point pattern `X`.

### Value

An object of class `"fv"` containing the estimated function.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

Rolf Turner r.turner@auckland.ac.nz

and Ege Rubak rubak@math.aau.dk

### See Also

`Kest`

### Examples

     K <- Ksector(swedishpines, 0, 90)
     plot(K)

[Package spatstat.core version 2.3-1 Index]