as.ppp

From spatstat v1.4-3 by Adrian Baddeley

Convert Data To Class ppp

Tries to coerce any reasonable kind of data to a point pattern (an object of class "ppp") for use by the spatstat package).

Keywords: spatial

Usage

as.ppp(X)
  as.ppp(X, W)
  as.ppp(X, fatal=TRUE)

Arguments

X: Data which will be converted into a point pattern
W: Data which define a default window for the pattern
fatal: Logical value. See Details.

Details

This function tries to coerce the data X to a point pattern (an object of class "ppp"; see ppp.object for an overview). The optional argument W is a default window for the pattern; it is used only if a window is not specified in X.

The data X may be:

an object of class"ppp"
an object of class"spp"as defined in thespatiallibrary
an object of class"quad"representing a quadrature scheme (seequad.object)
a two-column matrix
a structure with entriesx,y

In the last two cases, we need the second argument W which is converted to a window object by the function as.owin. In the first three cases, W will be ignored.

The argument fatal indicates what to do when W is missing and X contains no information about the window. If fatal=TRUE, a fatal error will be generated; if fatal=FALSE, the value NULL is returned.

An spp object is the representation of a point pattern in the spatial library. Our implementation recognises the following formats:

a structure with entriesx,yxl,xu,yl,yu
a structure with entriesx,yandarea, whereareais a structure with entriesxl,xu,yl,yu

(used in spatial versions 1 to 6 and version 7.1 respectively) where x and y are vectors of equal length giving the point coordinates, and xl, xu, yl, yu are numbers giving the dimensions of a rectangular window.

Point pattern datasets can also be created by the function ppp.

Value

An object of class "ppp" (see ppp.object) describing the point pattern and its window of observation. The value NULL may also be returned; see Details.

synopsis

as.ppp(X, W=NULL, fatal=TRUE)

Warnings

If the format of spp objects is changed in future versions of the spatial library, then as.ppp may not be able to interpret them. It currently handles all versions of spatial up to 7.1-4.

Examples

library(spatstat)

 plot(c(0,1),c(0,1),type="n")
 xy <- locator(20) # click on 20 points in plot window
 pp <- as.ppp(xy, c(0,1,0,1))
 
 w <- owin(c(0,1),c(0,1))
 plot(w)                      # neater
 xy <- locator(20)            # click on 20 points in plot window
 pp <- as.ppp(xy, w) 
 
 xy <- matrix(runif(40), ncol=2)
 pp <- as.ppp(xy, c(0,1,0,1))
 
 # Venables-Ripley format
 require(spatial)
 towns <- ppinit("towns.dat")
 pp <- as.ppp(towns)   # converted to our format
 detach(package:spatial)

Documentation reproduced from package spatstat, version 1.4-3, License: GPL version 2 or newer

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