spatstat (version 1.16-1)

# bdist.pixels: 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

w
A window (object of class "owin").
...
Arguments passed to as.mask to determine the pixel resolution.
coords
Logical: if TRUE, the result can be displayed using persp, contour etc.

## 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 $m \times n$ 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.

## 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.

owin.object, erosion, bdist.points,

## Examples

Run this code
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

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