ads (version 1.5-5)

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)
ppp2spp(p)

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.

p

a "ppp" object from package spatstat.geom.

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.

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 argument marks is not given.

• multivariate pattern: marks is 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 argument int2fac = TRUE.

• marked pattern: marks is a vector of real numbers attached to points of the pattern. Integer values may also be considered as numerical values if argument int2fac = FALSE.

References

Goreaud, F. and P?Pelissier, 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

# NOT RUN {
	data(BPoirier)
	BP <- BPoirier
	
# }
# NOT RUN {
univariate pattern in a rectangle of size [0,110] x [0,90]
# }
# NOT RUN {
	swr <- spp(BP$trees, win=BP$rect)
	
# }
# NOT RUN {
an alternative using atomic vectors of point coordinates
# }
# NOT RUN {
	swr <- spp(BP$trees, win=BP$rect) 
	summary(swr)
	plot(swr)
	
	
# }
# NOT RUN {
univariate pattern in a circle with radius 50 centred on (55,45)
# }
# NOT RUN {
	swc <- spp(BP$trees, win=c(55,45,50))
	summary(swc)
	plot(swc)
	plot(swc, out=TRUE) # plot points outside the circle

	
# }
# NOT RUN {
multivariate pattern in a rectangle of size [0,110] x [0,90]
# }
# NOT RUN {
	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
	
	
# }
# NOT RUN {
marked pattern in a rectangle of size [0,110] x [0,90]
# }
# NOT RUN {
	swrn <- spp(BP$trees, win=BP$rect, marks=BP$dbh)
	summary(swrn)
	plot(swrn)
	
	
# }
# NOT RUN {
multivariate pattern in a complex sampling window
# }
# NOT RUN {
	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
	
	
	
# }
# NOT RUN {
converting a ppp object from spatstat.geom
# }
# NOT RUN {
	data(demopat)
	demo.spp<-ppp2spp(demopat)
	plot(demo.spp)
# }