as.owin: 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, ..., fatal=TRUE)

Arguments

Data specifying an observation window, in any of several formats described under Details below.

fatal

Logical flag determining what to do if the data cannot be converted to an observation window. See Details.

...

Ignored.

Value

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

synopsis

as.owin(W, ..., fatal=TRUE) ## S3 method for class 'owin': as.owin(W, \dots, fatal=TRUE) ## S3 method for class 'ppp': as.owin(W, \dots, fatal=TRUE) ## S3 method for class 'im': as.owin(W, \dots, fatal=TRUE) ## S3 method for class 'default': as.owin(W, \dots, fatal=TRUE)

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 entriesxrange,yrangespecifying 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 entriesxl,xu,yl,yuspecifying the$x$and$y$dimensions of a rectangle as(xmin, xmax) = (xl, xu)and(ymin, ymax) = (yl, yu). This will accept objects of classsppused in the Venables and Ripleyspatiallibrary.
an object of class"ppp"representing a point pattern. In this case, the object'swindowstructure 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 ofNA, signifying that the pixel lies outside the window, is transformed into the logical valueFALSE, which is the corresponding convention for window masks.

If the argument W is not in one of these formats and cannot be converted to a window, then an error will be generated (if fatal=TRUE) or a value of NULL will be returned (if fatal=FALSE).

The function as.owin is generic, with methods for "owin", "im" and "ppp" as well as the default method.

Examples

Run this code

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)

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