Nearest Neighbour Map on Linear Network
Compute the nearest neighbour function of a point pattern on a linear network.
## S3 method for class 'lpp': nnfun(X, ...)
- A point pattern on a linear network
(object of class
- Extra arguments are ignored.
The (geodesic) nearest neighbour function of a
X on a linear network
tells us which point of
X is closest to
any given location.
X is a point pattern on a linear network
the nearest neighbour function of
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
measured by the shortest path. In other words the value of
is the identifier or serial number of the closest point of
nnfun.lpp is a method for the generic command
for the class
"lpp" of point patterns on a linear network.
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
in the form
v <- f(x,y), where
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
tp are the local
coordinates on the network.
The result of
f <- nnfun(X) also belongs to the class
It can be printed and plotted immediately as shown in the Examples.
It can be converted to a pixel image
functionin the Rlanguage, with arguments
x,yand optional arguments
seg,tp. It also belongs to the class
"linfun"which has methods for
To compute the distance to the nearest neighbour, see
data(letterR) X <- runiflpp(3, simplenet) f <- nnfun(X) f plot(f)