SGCS-funs {SGCS}R Documentation

Connectivity function, Cumulative Connectivity function and Clustering Function.

Description

Statistical measures based on edges of a geometric graph structure over a given point pattern data.
Date: 2009-03-04
License: GPL v2 or later

The graph structure is in this version geometric graph, meaning points x and y are connected if ||x-y||<R for the given range parameter R. Notice that in clustering function, the R equals to the parameter r.

The main function is art1Fun, but the use of shortcuts confun, cumconfun and clustfun is highly encouraged.

Usage

confun(pp, R=NULL, h=NULL, ...)
cumconfun(pp, R=NULL, ...)
clustfun(pp, ...)
art1Fun(pp, r = NULL, funtype = 1, fpar = 0, toroidal = FALSE, dbg = FALSE, 
        doDists = FALSE, doWeights = FALSE, prepR = 0, relative = FALSE, 
        prepGraph = NULL, minusR = NULL, included = NULL, parvec = NULL)

Arguments

pp All: Point pattern object. ppp-objects from package spatstat are safe.
R confun, cumconfun: Connection radius of the graph. If NULL, R=1/sqrt(lambda).
h confun: Smoothing parameter in kernel-estimation. Box kernel width = 2h.
... Parametes for the function art1Fun:
r Vector of the range parameters in which to calculate the function value. if NULL, a range from 0 to 1/3 of window length is used.
funtype (shortcuts handle) Which function to calculate. confun=1, cumconfun=2, clustfun=3.
fpar (shortcuts handle) Additional function parameter(s): confun fpar=c(R,h), cumconfun fpar=R.
toroidal Toroidal correction of rectangular window.
dbg Print additional messages.
doDists Precalculate distances for faster computation. Be aware of memory consumption O(n^2).
doWeights Precalculate confun translation correction weights for faster computation. Be aware of memory consumption O(n^2).
prepR Preparation distance: If >0, precalculate a graph, from which it is easier to find needed connections. Useful with other graphs (in the future).
relative Scale the range parameter to a unit range, i.e. scale r with sqrt(pi*lambda). Good when comparing different phenomena in different spatial scales.
prepGraph An optional graph-object from spatgraphs to be used as basis for finding connections between points. Good for big datasets.
minusR Minus-correction parameter. Rectangular window required, NULL means no correction.
included Point pattern size boolean vector for inclusion of points in computation. NULL means all points.
parvec Same as r.

Value

An object of class graphfcl, which can be plotted with the generic plot-command. Contains the given parameters and calculated function values, and an simulation based estimation of Poisson values. Note that the Poisson values (and the limits drawn if flag limits=TRUE) is correct only when the R=1/sqrt(lambda).

Author(s)

Tuomas Rajala
University of Jyvaskyla, Finland
tarajala@maths.jyu.fi

References

Rajala, Penttinen: Spatial clustering and graph feature statistics (working title).


[Package SGCS version 0.9 Index]