raster.x: Cartesian Coordinates for a Pixel Raster

Description

Return the $x$ and $y$ coordinates of each pixel in a binary pixel image.

Usage

raster.x(w, drop=FALSE)
 raster.y(w, drop=FALSE)
 raster.xy(w, drop=FALSE)

Arguments

A window (object of class "owin") of type "mask" representing a binary pixel image.

drop

Logical. If TRUE, then coordinates of pixels that lie outside the window are removed. If FALSE (the default) then the coordinates of every pixel in the containing rectangle are retained.

Value

raster.xy returns a list with components x and y which are numeric vectors of equal length containing the pixel coordinates.
If drop=FALSE, raster.x and raster.y return a matrix of the same dimensions as the pixel grid in w, and giving the value of the $x$ (or $y$) coordinate of each pixel in the raster.
If drop=TRUE, raster.x and raster.y return numeric vectors.

Details

The argument w should be a window (an object of class "owin", see owin.object for details). A window of type "mask" represents a binary pixel image.

If drop=FALSE (the default), the functions raster.x and raster.y return a matrix of the same dimensions as the binary pixel image itself, with entries giving the $x$ coordinate (for raster.x) or $y$ coordinate (for raster.y) of each pixel in the binary image.

If drop=TRUE, pixels that lie outside the window w are removed, and raster.x and raster.y return numeric vectors containing the coordinates of the pixels that are inside the window w.

The function raster.xy returns a list with components x and y which are numeric vectors of equal length containing the pixel coordinates.

Examples

Run this code

u <- owin(c(-1,1),c(-1,1)) # square of side 2
  w <- as.mask(u, eps=0.01) # 200 x 200 grid
  X <- raster.x(w)
  Y <- raster.y(w)
  disc <- owin(c(-1,1), c(-1,1), mask=(X^2 + Y^2 <= 1))
  plot(disc)
  # approximation to the unit disc