Convert Data To Class owin

Description

Converts data specifying an observation window in any of several formats, into an object of class "owin".

Usage

 as.owin(W)

Arguments

Details

The class "owin" is a way of specifying the observation window for a point pattern. See owin.object for an overview.

This function converts data in any of several formats into an object of class "owin" for use by the spatstat package. The argument W may be

• an object of class "owin"
• a structure with entries xrange, yrange specifying the x and y dimensions of a rectangle
• a four-element vector (interpreted as (xmin, xmax, ymin, ymax)) specifying the x and y dimensions of a rectangle
• a structure with entries xl, xu, yl, yu specifying the x and y dimensions of a rectangle as (xmin, xmax) = (xl, xu) and (ymin, ymax) = (yl, yu). This will accept objects of class spp used in the Venables and Ripley spatial library.
• an object of class "ppp" representing a point pattern. In this case, the object's window structure will be extracted.
• an object of class "im" representing a pixel image. In this case, a window of type "mask" will be returned, with the same pixel raster coordinates as the image. An image pixel value of NA, signifying that the pixel lies outside the window, is transformed into the logical value FALSE, which is the corresponding convention for window masks.

Value

An object of class "owin" (see owin.object) specifying an observation window.

Author(s)

Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf

See Also

owin.object, owin

Examples

 w <- as.owin(c(0,1,0,1))
 w <- as.owin(list(xrange=c(0,5),yrange=c(0,10)))
 # point pattern
 data(demopat)
 w <- as.owin(demopat)
 # image
 Z <- as.im(function(x,y) { x + 3}, unit.square())
 w <- as.owin(Z)

 # Venables & Ripley 'spatial' package
 require(spatial)
 towns <- ppinit("towns.dat")
 w <- as.owin(towns)
 detach(package:spatial)