Distance to Boundary of Window
Computes the distances from each pixel in a window to the boundary of the window.
bdist.pixels(w, ..., style="image")
- A window (object of class
- Arguments passed to
as.maskto determine the pixel resolution.
- Character string determining the format of
the output: either
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
as.mask to determine the pixel resolution.
style="image", a pixel image (object of class
"im") containing the distances from each pixel in the image raster to the boundary of the window.If
style="matrix", 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
style="coords", a list with three components
x,yare vectors of length $m,n$ giving the $x$ and $y$ coordinates respectively, and
zis 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
u <- owin(c(0,1),c(0,1)) d <- bdist.pixels(u, eps=0.01) image(d) d <- bdist.pixels(u, eps=0.01, style="matrix") mean(d >= 0.1) # value is approx (1 - 2 * 0.1)^2 = 0.64