spokes {spatstat} | R Documentation |
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.
spokes(x, y, nrad = 3, nper = 3, fctr = 1.5, Mdefault = 1)
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.
|
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
.
A list with two components x
and y
, which are numeric
vectors giving the coordinates of the dummy points.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf
quad.object
,
quadscheme
,
inside.owin
,
gridcentres
,
stratrand
library(spatstat) dat <- runifrect(10) plot(dat) dum <- spokes(dat$x, dat$y) points(dum$x, dum$y, pch=".") Q <- quadscheme(dat, dum)