lineardisc(L, x = locator(1), r, plotit = TRUE,
cols=c("blue", "red","green")) countends(L, x = locator(1), r, toler=NULL)
"linnet"
)."ppp"
)
containing exactly 1 point, or a numeric vector of length 2.countends
. See Details.
There is a sensible default.lineardisc
is a list with two entries:"psp"
)
representing the interior disc"ppp"
)
representing the relative boundary of the disc.countends
is an integer giving the number of
points in the relative boundary. 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 $r$.
The function 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 optional threshold toler
is used to suppress numerical
errors in countends
.
If the distance from $u$ to a network vertex $v$
is between r-toler
and r+toler
, the vertex
will be treated as lying on the relative boundary.
linnet
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
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