R: Class owin

owin.object {spatstat} | R Documentation

## Class owin

### Description

A class `owin` to define the “observation window” of a point pattern

### Details

In the spatstat library, a point pattern dataset must include information about the window or region in which the pattern was observed. A window is described by an object of class `"owin"`. Windows of arbitrary shape are supported.

An object of class `"owin"` has one of three types:

`"rectangle"`: | a rectangle in the two-dimensional plane with edges parallel to the axes
`"polygonal"`: | a region whose boundary is a polygon or several polygons. The region may have holes and may consist of several disconnected pieces.
`"mask"`: | a binary image (a logical matrix) set to `TRUE` for pixels inside the window and `FALSE` outside the window.

Objects of class `"owin"` may be created by the function `owin` and converted from other types of data by the function `as.owin`.

They may be manipulated by the functions `as.rectangle`, `as.mask`, `complement.owin`, `rotate`, `shift`, `affine`, `erosion`, `dilation`, `opening` and `closing`.

Geometrical calculations available for windows include `area.owin`, `perimeter`, `diameter.owin`, `boundingbox`, `eroded.areas`, `bdist.points`, `bdist.pixels`, and `even.breaks.owin`. The mapping between continuous coordinates and pixel raster indices is facilitated by the functions `raster.x`, `raster.y` and `nearest.raster.point`.

There is a `plot` method for window objects, `plot.owin`. This may be useful if you wish to plot a point pattern's window without the points for graphical purposes.

There are also methods for `summary` and `print`.

### Warnings

In a window of type `"mask"`, the row index corresponds to increasing y coordinate, and the column index corresponds to increasing x coordinate.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

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

### See Also

`owin`, `as.owin`, `as.rectangle`, `as.mask`, `summary.owin`, `print.owin`, `complement.owin`, `erosion`, `dilation`, `opening`, `closing`, `affine.owin`, `shift.owin`, `rotate.owin`, `raster.x`, `raster.y`, `nearest.raster.point`, `plot.owin`, `area.owin`, `boundingbox`, `diameter`, `eroded.areas`, `bdist.points`, `bdist.pixels`

### Examples

     w <- owin()
     w <- owin(c(0,1), c(0,1))
     # the unit square

     w <- owin(c(0,1), c(0,2))
     ## Not run:
     if(FALSE) {
       plot(w)
       # plots edges of a box 1 unit x 2 units
       v <- locator()
       # click on points in the plot window
       # to be the vertices of a polygon
       # traversed in anticlockwise order
       u <- owin(c(0,1), c(0,2), poly=v)
       plot(u)
       # plots polygonal boundary using polygon()
       plot(as.mask(u, eps=0.02))
       # plots discrete pixel approximation to polygon
     }

    ## End(Not run)

[Package spatstat version 1.63-3 Index]