createxymap: Create map objects for some points and a given distance
Description
Creates a map object from a list of coordinates by treating observations within a certain distance as neighbors.
The resulting neighborhood structure is stored in a map object in graph format while a map
in boundary format is created to enable visualisation.
Usage
createxymap(x, y, districts=NULL, p=2, max.dist)
Value
List of two elements: map object in graph format and map object in boundary format.
Arguments
x
Vector of x-coordinates of underlying points
y
Vector of y-coordinates of underlying points
districts
Either NULL or a vector of names for labeling points. If districts=NULL, points are labelled by index.
p
Any p-norm with p>=1 can be chosen as the distance measure with the Euclidian distance (p=2) being the default. For p=Inf, the maximum of coordinates is used. Except for p=Inf, calculations can fail for huge p.
max.dist
Value which determines the neighborship. Points whose distance is smaller or equal than max.dist are considered as neighbors.
x <- c(3,3,5,9.5,11,11)
y <- c(2,4,4,6,4.5,5)
xymap <- createxymap(x, y, districts=c("A","B","C","D","E","F"), max.dist=2)
xymap$gra
drawmap(map=xymap$bnd)