# nnfun.lpp

0th

Percentile

##### Nearest Neighbour Map on Linear Network

Compute the nearest neighbour function of a point pattern on a linear network.

Keywords
spatial, math
##### Usage
# S3 method for lpp
nnfun(X, ..., k=1)
##### Arguments
X

A point pattern on a linear network (object of class "lpp").

k

Integer. The algorithm finds the kth nearest neighbour in X from any spatial location.

Other 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 R language, 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 a vector of identifiers or serial numbers of the data points closest to these spatial 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 R language, with arguments x,y and optional arguments seg,tp. It also belongs to the class "linfun" which has methods for plot, print etc.

##### See Also

linfun, methods.linfun.

To compute the distance to the nearest neighbour, see distfun.lpp.

• nnfun.lpp
##### Examples
# NOT RUN {
data(letterR)
X <- runiflpp(3, simplenet)
f <- nnfun(X)
f
plot(f)
# }

Documentation reproduced from package spatstat, version 1.49-0, License: GPL (>= 2)

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