rSPDistance: Randomized shortest path distance

Description

Calculates the randomized shortest path distance between points.

Usage

rSPDistance(x, from, to, theta, totalNet = "net", method = 1)

Value

distance matrix (S3 class dist or matrix)

Arguments

x: TransitionLayer object
from: point locations coordinates (of SpatialPoints, matrix or numeric class)
to: point locations coordinates (of SpatialPoints, matrix or numeric class)
theta: theta is the degree from which the path randomly deviates from the shortest path, 0 < theta < 20
totalNet: total or net movements between cells
method: method 1 (as defined in Saerens et al.) or method 2 (a modified version, see below in Details)

Author

Jacob van Etten

Details

The function implements the algorithm given by Saerens et al. (2009).

Method 1 implements the method as it is. Method 2 uses W = exp(-theta * ln(P)).

References

Saerens M., L. Yen, F. Fouss, and Y. Achbany. 2009. Randomized shortest-path problems: two related models. Neural Computation, 21(8):2363-2404.

Examples

Run this code

#Create a new raster and set all its values to unity.
r <- raster(nrows=18, ncols=36) 
r <- setValues(r,rep(1,ncell(raster)))

#Create a Transition object from the raster
tr <- transition(r,mean,4)

#Create two sets of coordinates
sP1 <- SpatialPoints(cbind(c(65,5,-65),c(55,35,-35)))
sP2 <- SpatialPoints(cbind(c(50,15,-40),c(80,20,-5)))

#Calculate the RSP distance between the points
rSPDistance(tr, sP1, sP2, 1)

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