inside.owin {spatstat}R Documentation

Test Whether Points Are Inside A Window

Description

Test whether points lie inside or outside a given window.

Usage

 inside.owin(x, y, w)

Arguments

x Vector of x coordinates of points to be tested.
y Vector of y coordinates of points to be tested.
w A window. This should be an object of class owin, or can be given in any format acceptable to as.owin().

Details

This function tests whether each of the points (x[i],y[i]) lies inside or outside the window w and returns TRUE if it is inside.

The boundary of the window is treated as being inside.

If w is of type "rectangle" or "polygonal", the algorithm uses analytic geometry (the discrete Stokes theorem). Computation time is linear in the number of points and (for polygonal windows) in the number of vertices of the boundary polygon. Boundary cases are correct to single precision accuracy.

If w is of type "mask" then the pixel closest to (x[i],y[i]) is tested. The results may be incorrect for points lying within one pixel diameter of the window boundary.

Value

Logical vector whose ith entry is TRUE if the corresponding point (x[i],y[i]) is inside w.

Author(s)

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

See Also

owin.object, as.owin

Examples

  # hexagonal window
  k <- 6
  theta <- 2 * pi * (0:(k-1))/k
  co <- cos(theta)
  si <- sin(theta)
  mas <- owin(c(-1,1), c(-1,1), poly=list(x=co, y=si))
  ## Not run: 
  plot(mas)
  
## End(Not run)

  # random points in rectangle
  x <- runif(30,min=-1, max=1)
  y <- runif(30,min=-1, max=1)

  ok <- inside.owin(x, y, mas)

  ## Not run: 
  points(x[ok], y[ok])
  points(x[!ok], y[!ok], pch="x")
  
## End(Not run)
[Package spatstat version 1.11-3 Index]