ads (version 1.4)

spp: Creating a spatial point pattern

Description

Function spp creates an object of class "spp", which represents a spatial point pattern observed in a finite sampling window (or study region). The ads library supports univariate, multivariate and marked point patterns observed in simple (rectangular or circular) or complex sampling windows.

Usage

spp(x, y=NULL, window, triangles, marks, int2fac=TRUE)

Arguments

x,y

if y=NULL, $x$ is a list of two vectors of point coordinates, else both $x$ and $y$ are atomic vectors of point coordinates.

window

a "swin" object or a vector defining the limits of a simple sampling window: c(xmin,ymin,xmax,ymax) for a rectangle ; c(x0,y0,r0) for a circle.

triangles

(optional) a list of triangles removed from a simple initial window to define a complex sampling window (see swin).

marks

(optional) a vector of mark values, which may be factor levels or numerical values (see Details).

int2fac

if TRUE, integer marks are automatically coerced into factor levels.

Value

• An object of class "spp" describing a spatial point pattern observed in a given sampling window.
• $type
  a character string indicating if the spatial point pattern is "univariate", "multivariate" or "marked".
• $window
  an swin object describing the sampling window (see swin).
• $n
  an integer value giving the number of points of the pattern located inside the sampling window (points on the boundary are considered to be inside).
• $x
  a vector of $x$ coordinates of points located inside the sampling window.
• $y
  a vector of $y$ coordinates of points located inside the sampling window.
• $nout
  (optional) an integer value giving the number of points of the pattern located outside the sampling window.
• $xout
  (optional) a vector of $x$ coordinates of points located outside the sampling window.
• $yout
  (optional) a vector of $y$ coordinates of points located outside the sampling window.
• $marks
  (optional) a vector of the marks attached to points located inside the sampling window.
• $marksout
  (optional) a vector of the marks attached to points located outside the sampling window.

encoding

latin1

Details

A spatial point pattern is assumed to have been observed within a specific sampling window (a finite study region) defined by the window argument. If window is a simple "swin" object, it may be coerced into a complex type by adding a triangles argument (see swin). A spatial point pattern may be of 3 different types.

• univariate pattern:by default when argumentmarksis not given.
• multivariate pattern:marksis a factor, which levels are interpreted as categorical marks (e.g. colours, species, etc.) attached to points of the pattern. Integer marks may be automatically coerced into factor levels when argumentint2fac = TRUE.
• marked pattern:marksis a vector of real numbers attached to points of the pattern. Integer values may also be considered as numerical values if argumentint2fac = FALSE.

References

Goreaud, F. and P�lissier, R. 1999. On explicit formula of edge effect correction for Ripley's K-function. Journal of Vegetation Science, 10:433-438.

See Also

plot.spp, swin

Examples

data(BPoirier)
	BP <- BPoirier
	# univariate pattern in a rectangle of size [0,110] x [0,90]
	swr <- spp(BP$trees, win=BP$rect)
	# an alternative using atomic vectors of point coordinates
	#swr <- spp(BP$trees, win=BP$rect) 
	summary(swr)
	plot(swr)
	
	# univariate pattern in a circle with radius 50 centred on (55,45)
	swc <- spp(BP$trees, win=c(55,45,50))
	summary(swc)
	plot(swc)
	plot(swc, out=TRUE) # plot points outside the circle

	# multivariate pattern in a rectangle of size [0,110] x [0,90]
	swrm <- spp(BP$trees, win=BP$rect, marks=BP$species)
	summary(swrm)
	plot(swrm)
	plot(swrm, chars=c("b","h","o")) # replace symbols by letters
	
	# marked pattern in a rectangle of size [0,110] x [0,90]
	swrn <- spp(BP$trees, win=BP$rect, marks=BP$dbh)
	summary(swrn)
	plot(swrn)
	
	# multivariate pattern in a complex sampling window
	swrt <- spp(BP$trees, win=BP$rect, tri=BP$tri1, marks=BP$species)
	summary(swrt)
	plot(swrt)
	plot(swrt, out=TRUE) # plot points outside the sampling window
	
	
	#converting a ppp object from spatstat
	data(demopat)
	demo.spp<-ppp2spp(demopat)
	plot(demo.spp)