spatstat (version 1.48-0)

rstrat: Simulate Stratified Random Point Pattern

Description

Generates a ``stratified random'' pattern of points in a window, by dividing the window into rectangular tiles and placing k random points independently in each tile.

Usage

rstrat(win=square(1), nx, ny=nx, k = 1, 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 tiles in each column.

ny

Number of tiles in each row.

k

Number of random points to generate in each tile.

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.

Value

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

Details

This function generates a random pattern of points in a ``stratified random'' sampling design. It can be useful for generating random spatial sampling points.

The bounding rectangle of win is divided into a regular $nx * ny$ grid of rectangular tiles. In each tile, k random points are generated independently with a uniform distribution in that tile.

Some of these 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.

See Also

rsyst, runifpoint, quadscheme

Examples

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

  # polygonal boundary
  data(letterR)
  X <- rstrat(letterR, 5, 10, k=3)
  plot(X)