R: Cartesian Coordinates for a Pixel Raster

raster.x {spatstat.geom} | R Documentation

## Cartesian Coordinates for a Pixel Raster

### Description

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

### Usage

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

### Arguments

`w` | A pixel image (object of class `"im"`) or a mask window (object of class `"owin"` of type `"mask"`).
`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.

### Details

The argument `w` should be either a pixel image (object of class `"im"`) or a mask window (an object of class `"owin"` of type `"mask"`).

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

If `drop=TRUE`, pixels that lie outside the window `w` (or outside the domain of the image `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.

### 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.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au , Rolf Turner r.turner@auckland.ac.nz

and Ege Rubak rubak@math.aau.dk

### See Also

`owin`, `as.mask`, `pixelcentres`

### Examples

      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

[Package spatstat.geom version 2.2-0 Index]