spokes

Spokes pattern of dummy points

Generates a pattern of dummy points in a window, given a data point pattern. The dummy points lie on the radii of circles emanating from each data point.

Usage

spokes(x, y, nrad = 3, nper = 3, fctr = 1.5, Mdefault = 1)

Details

This function is useful in creating dummy points for quadrature schemes (see quadscheme).

Given the point pattern specified by the vectors x and y, the function creates a pattern of nrad * nper * length(x) dummy points.

Around each data point (x[i],y[i]) there are nrad * nper dummy points, lying on nrad radii emanating from (x[i],y[i]), with nper dummy points equally spaced along each radius.

The (equal) spacing of dummy points along each radius is controlled by the factor fctr. The distance from a data point to the furthest of its associated dummy points is fctr * M where M is the mean nearest neighbour distance for the data points.

If the point pattern specified by x and y contains only one point, the nearest neighbour distance is infinite, so the value Mdefault will be used in place of M.

See Also

quad.object, quadscheme, inside.owin, gridcentres, stratrand

Aliases

• spokes

Examples

library(spatstat)
  dat <- runifrect(10)
  plot(dat)
  dum <- spokes(dat$x, dat$y)
  points(dum$x, dum$y, pch=".")
  Q <- quadscheme(dat, dum)