# bdist.pixels

0th

Percentile

##### Distance to Boundary of Window

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

Keywords
spatial, math
##### Usage
bdist.pixels(w, ..., style="image")
##### Arguments
w
A window (object of class "owin").
...
Arguments passed to as.mask to determine the pixel resolution.
style
Character string determining the format of the output: either "matrix", "coords" or "image".
##### Details

This function computes, for each pixel $u$ in the window w, the shortest distance $d(u, W^c)$ 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 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,y,z, where x,y are vectors of length $m,n$ giving the $x$ and $y$ coordinates respectively, and z is an $m \times n$ 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.

owin.object, erosion, bdist.points, bdist.tiles.

• bdist.pixels
##### 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, style="matrix")
mean(d >= 0.1)
# value is approx (1 - 2 * 0.1)^2 = 0.64
Documentation reproduced from package spatstat, version 1.37-0, License: GPL (>= 2)

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