R: Simulate systematic random point pattern

rsyst {spatstat.geom} | R Documentation

## Simulate systematic random point pattern

### Description

Generates a “systematic random” pattern of points in a window, consisting of a grid of equally-spaced points with a random common displacement.

### Usage

     rsyst(win=square(1), nx=NULL, ny=nx, ..., dx=NULL, dy=dx,
           nsim=1, drop=TRUE)

### Arguments

`win` | A window. An object of class `owin`, or data in any format acceptable to `as.owin()`.
`nx` | Number of columns of grid points in the window. Incompatible with `dx`.
`ny` | Number of rows of grid points in the window. Incompatible with `dy`.
`...` | Ignored.
`dx` | Spacing of grid points in x direction. Incompatible with `nx`.
`dy` | Spacing of grid points in y direction. Incompatible with `ny`.
`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

This function generates a “systematic random” pattern of points in the window `win`. The pattern consists of a rectangular grid of points with a random common displacement.

The grid spacing in the x direction is determined either by the number of columns `nx` or by the horizontal spacing `dx`. The grid spacing in the y direction is determined either by the number of rows `ny` or by the vertical spacing `dy`.

The grid is then given a random displacement (the common displacement of the grid points is a uniformly distributed random vector in the tile of dimensions `dx, dy`).

Some of the resulting grid points may lie outside the window `win`: if they do, they are deleted. The result is a point pattern inside the window `win`.

This function is useful in creating dummy points for quadrature schemes (see `quadscheme`) as well as in simulating random point patterns.

### Value

A point pattern (an object of class `"ppp"`) if `nsim=1`, or a list of point patterns if `nsim > 1`.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

and Rolf Turner r.turner@auckland.ac.nz

### See Also

`rstrat`, `runifpoint`, `quadscheme`

### Examples

      X <- rsyst(nx=10)
      plot(X)

      # polygonal boundary
      X <- rsyst(letterR, 5, 10)
      plot(X)

[Package spatstat.geom version 2.2-0 Index]