nnfun.lpp
Nearest Neighbour Map on Linear Network
Compute the nearest neighbour function of a point pattern on a linear network.
Usage
## S3 method for class 'lpp':
nnfun(X, ...)
Arguments
- X
- A point pattern on a linear network
(object of class
"lpp"
). - ...
- Extra arguments are ignored.
Details
The (geodesic) nearest neighbour function of a
point pattern X
on a linear network L
tells us which point of X
is closest to
any given location.
If X
is a point pattern on a linear network L
,
the nearest neighbour function of X
is the mathematical function $f$ defined for any
location $s$ on the network by f(s) = i
, where
X[i]
is the closest point of X
to the location s
measured by the shortest path. In other words the value of f(s)
is the identifier or serial number of the closest point of X
.
The command nnfun.lpp
is a method for the generic command
nnfun
for the class "lpp"
of point patterns on a linear network.
If X
is a point pattern on a linear network,
f <- nnfun(X)
returns a function
in the Rlanguage, with arguments x,y, ...
, that represents the
nearest neighbour function of X
. Evaluating the function f
in the form v <- f(x,y)
, where x
and y
are any numeric vectors of equal length containing coordinates of
spatial locations, yields the values of the distance function at these
locations. More efficiently f
can take the arguments
x, y, seg, tp
where seg
and tp
are the local
coordinates on the network.
The result of f <- nnfun(X)
also belongs to the class
"linfun"
.
It can be printed and plotted immediately as shown in the Examples.
It can be converted to a pixel image
using as.linim
.
Value
- A
function
in the Rlanguage, with argumentsx,y
and optional argumentsseg,tp
. It also belongs to the class"linfun"
which has methods forplot
,print
etc.
See Also
To compute the distance to the nearest neighbour, see
distfun.lpp
.
Examples
data(letterR)
X <- runiflpp(3, simplenet)
f <- nnfun(X)
f
plot(f)