Compute Disc of Given Radius in Linear Network
lineardisc(L, x = locator(1), r, plotit = TRUE, cols=c("blue", "red","green")) countends(L, x = locator(1), r)
- Linear network (object of class
- Location of centre of disc.
Either a point pattern (object of class
"ppp") containing exactly 1 point, or a numeric vector of length 2.
- Radius of disc.
- Logical. Whether to plot the disc.
- Colours for plotting the disc. A numeric or character vector of length 3 specifying the colours of the disc centre, disc lines and disc endpoints respectively.
The relative boundary of the disc $B(u,r)$
is the set of points $v$ such that the shortest path distance from
$x$ to $u$ is equal to $r$.
lineardisc computes the
disc of radius $r$ and its relative boundary,
optionally plots them, and returns them.
The faster function
countends simply counts the number of
points in the relative boundary.
- The value of
lineardiscis a list with two entries:
lines Line segment pattern (object of class
"psp") representing the interior disc
endpoints Point pattern (object of class
"ppp") representing the relative boundary of the disc.
- The value of
countendsis an integer giving the number of points in the relative boundary.
Ang, Q.W. (2010) Statistical methodology for events on a network. Master's thesis, School of Mathematics and Statistics, University of Western Australia. Ang, Q.W., Baddeley, A. and Nair, G. (2012) Geometrically corrected second-order analysis of events on a linear network, with applications to ecology and criminology. Scandinavian Journal of Statistics 39, 591--617.
example(linnet) lineardisc(letterA, c(0,3), 1.6) # count the endpoints countends(letterA, c(0,3), 1.6) # cross-check (slower) lineardisc(letterA, c(0,3), 1.6, plotit=FALSE)$endpoints$n