R: Take Complement of a Window

complement.owin {spatstat} | R Documentation

## Take Complement of a Window

### Description

Take the set complement of a window, within its enclosing rectangle or in a larger rectangle.

### Usage

     complement.owin(w, frame=as.rectangle(w))

### Arguments

`w` | an object of class `"owin"` describing a window of observation for a point pattern.
`frame` | Optional. The enclosing rectangle, with respect to which the set complement is taken.

### Details

This yields a window object (of class `"owin"`, see `owin.object`) representing the set complement of `w` with respect to the rectangle `frame`.

By default, `frame` is the enclosing box of `w` (originally specified by the arguments `xrange` and `yrange` given to `owin` when `w` was created). If `frame` is specified, it must be a rectangle (an object of class `"owin"` whose type is `"rectangle"`) and it must be larger than the enclosing box of `w`. This rectangle becomes the enclosing box for the resulting window.

If `w` is a rectangle, then `frame` must be specified. Otherwise an error will occur (since the complement of `w` in itself is empty).

For rectangular and polygonal windows, the complement is computed by reversing the sign of each boundary polygon, while for binary masks it is computed by negating the pixel values.

### Value

Another object of class `"owin"` representing the complement of the window, i.e. the inside of the window becomes the outside.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

and Rolf Turner r.turner@auckland.ac.nz

### See Also

`owin`, `owin.object`

### Examples

       # rectangular
       a <- owin(c(0,1),c(0,1))
       b <- owin(c(-1,2),c(-1,2))
       bmina <- complement.owin(a, frame=b)
       # polygonal
       data(demopat)
       w <- Window(demopat)
       outside <- complement.owin(w)
       # mask
       w <- as.mask(Window(demopat))
       outside <- complement.owin(w)

[Package spatstat version 1.63-3 Index]