distfun.lpp

0th

Percentile

Distance Map on Linear Network

Compute the distance function of a point pattern on a linear network.

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

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

k

An integer. The distance to the kth nearest point will be computed.

Extra arguments are ignored.

Details

On a linear network $L$, the “geodesic distance function” of a set of points $A$ in $L$ is the mathematical function $f$ such that, for any location $s$ on $L$, the function value f(s) is the shortest-path distance from $s$ to $A$.

The command distfun.lpp is a method for the generic command distfun for the class "lpp" of point patterns on a linear network.

If X is a point pattern on a linear network, f <- distfun(X) returns a function in the R language that represents the distance 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 be called in the form v <- f(x, y, seg, tp) where seg and tp are the local coordinates on the network. It can also be called as v <- f(x) where x is a point pattern on the same linear network.

The function f obtained from f <- distfun(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 with arguments x,y and optional arguments seg,tp. It also belongs to the class "linfun" which has methods for plot, print etc.

linfun, methods.linfun.

To identify which point is the nearest neighbour, see nnfun.lpp.

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

# using a distfun as a covariate in a point process model:
Y <- runiflpp(4, simplenet)
fit <- lppm(Y ~D, covariates=list(D=f))

f(Y)
# }

Documentation reproduced from package spatstat, version 1.57-1, License: GPL (>= 2)

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