R: Random Perturbation of a Point Pattern

rjitter {spatstat.geom} | R Documentation

## Random Perturbation of a Point Pattern

### Description

Applies independent random displacements to each point in a point pattern.

### Usage

    rjitter(X, ...)

    ## S3 method for class 'ppp'
    rjitter(X, radius, retry=TRUE, giveup = 10000, ..., nsim=1, drop=TRUE)

### Arguments

`X` | A point pattern (object of class `"ppp"`).
`radius` | Scale of perturbations. A positive numerical value. The displacement vectors will be uniformly distributed in a circle of this radius. There is a sensible default. Alternatively, `radius` may be a numeric vector of length equal to the number of points in `X`, giving a different displacement radius for each data point.
`retry` | What to do when a perturbed point lies outside the window of the original point pattern. If `retry=FALSE`, the point will be lost; if `retry=TRUE`, the algorithm will try again.
`giveup` | Maximum number of unsuccessful attempts.
`...` | Ignored.
`nsim` | Number of simulated realisations to be generated.
`drop` | Logical. If `nsim=1` and `drop=TRUE` (the default), the result will be a point pattern, rather than a list containing a point pattern.

### Details

The function `rjitter` is generic, with methods for point patterns (described here) and for some other types of geometrical objects.

Each of the points in the point pattern `X` is subjected to an independent random displacement. The displacement vectors are uniformly distributed in a circle of radius `radius`.

If a displaced point lies outside the window, then if `retry=FALSE` the point will be lost.

However if `retry=TRUE`, the algorithm will try again: each time a perturbed point lies outside the window, the algorithm will reject it and generate another proposed perturbation of the original point, until one lies inside the window, or until `giveup` unsuccessful attempts have been made. In the latter case, any unresolved points will be included without any perturbation. The return value will always be a point pattern with the same number of points as `X`.

### Value

The result of `rjitter.ppp` is a point pattern (an object of class `"ppp"`) or a list of point patterns.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.

### Examples

       X <- rsyst(owin(), 10, 10)
       Y <- rjitter(X, 0.02)
       plot(Y)
       Z <- rjitter(X)

[Package spatstat.geom version 2.3-2 Index]