stratrand {spatstat} | R Documentation |
Generates a “stratified random” pattern of points in a window,
by dividing the window into rectangular tiles and placing
k
random points in each tile.
stratrand(window, nx, ny, k = 1)
window |
A window.
An object of class |
nx |
Number of tiles in each row. |
ny |
Number of tiles in each column. |
k |
Number of random points to generate in each tile. |
The bounding rectangle of window
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.
Note that some of these grid points may lie outside the window,
if window
is not of type "rectangle"
. The function
inside.owin
can be used to select those grid points
which do lie inside the window. See the examples.
This function is useful in creating dummy points for quadrature
schemes (see quadscheme
) as well as in simulating
random point patterns.
A list with two components x
and y
, which are numeric
vectors giving the coordinates of the random points.
Adrian Baddeley Adrian.Baddeley@curtin.edu.au
and Rolf Turner r.turner@auckland.ac.nz
quad.object
,
quadscheme
,
inside.owin
,
gridcentres
w <- unit.square() xy <- stratrand(w, 10, 10) ## Not run: plot(w) points(xy) ## End(Not run) # polygonal boundary bdry <- list(x=c(0.1,0.3,0.7,0.4,0.2), y=c(0.1,0.1,0.5,0.7,0.3)) w <- owin(c(0,1), c(0,1), poly=bdry) xy <- stratrand(w, 10, 10, 3) ## Not run: plot(w) points(xy) ## End(Not run) # determine which grid points are inside polygon ok <- inside.owin(xy$x, xy$y, w) ## Not run: plot(w) points(xy$x[ok], xy$y[ok]) ## End(Not run)