spatstat (version 1.3-2)

as.ppp: Convert Data To Class ppp

Description

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

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.

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)

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 used in the Venables and Ripley packagespatial
• an object of class"quad"representing a quadrature scheme (seequad.object)
• a structure with entriesx,y(vectors of equal length) andxl,xu,yl,yu(numbers giving the dimensions of a rectangular window)
• 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.

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

See Also

ppp, ppp.object, as.owin, owin.object

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
 sp <- list(x=runif(10), y=runif(10), xl=0, xu=1, yl=0, yu=1)
 pp <- as.ppp(sp)   # converted to our format