spokes

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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.

Keywords
spatial
Usage
spokes(x, y, nrad = 3, nper = 3, fctr = 1.5, Mdefault = 1)
Arguments
x
Vector of $x$ coordinates of data points.
y
Vector of $y$ coordinates of data points.
nrad
Number of radii emanating from each data point.
nper
Number of dummy points per radius.
fctr
Scale factor. Length of largest spoke radius is fctr * M where M is the mean nearest neighbour distance for the data points.
Mdefault
Value of M to be used if x has length 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.

Value

  • A list with two components x and y, which are numeric vectors giving the coordinates of the dummy points.

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)
Documentation reproduced from package spatstat, version 1.4-3, License: GPL version 2 or newer

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