Distance to Boundary of Window

Description

Computes the distances from each pixel in a window to the boundary of the window.

Usage

 bdist.pixels(w, ..., coords=TRUE)

Arguments

Details

This function computes, for each pixel u in the window w, the shortest distance dist(u, W') from u to the boundary of W.

If the window is not of type "mask" then it is first converted to that type. The arguments "..." are passed to as.mask to determine the pixel resolution.

Value

If coords is false, a matrix giving the distances from each pixel in the image raster to the boundary of the window. Rows of this matrix correspond to the y coordinate and columns to the x coordinate.
If coords is true, a list with three components x,y,z, where x,y are vectors of length m,n giving the x and y coordinates respectively, and z is an m x n matrix such that z[i,j] is the distance from (x[i],y[j]) to the boundary of the window. Rows of this matrix correspond to the x coordinate and columns to the y coordinate. This result can be plotted with persp, image or contour.

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, erode.owin, bdist.points,

Examples

  u <- owin(c(0,1),c(0,1))
  d <- bdist.pixels(u, eps=0.01)
  image(d)
  d <- bdist.pixels(u, eps=0.01, coords=FALSE)
  mean(d >= 0.1)
  # value is approx (1 - 2 * 0.1)^2 = 0.64