costDistance: Cost distance (least-cost distance)

In gdistance: Distances and Routes on Geographical Grids

Description

Calculate the least-cost distance between points.

Usage

costDistance(x, fromCoords, toCoords)

Arguments

x	object of class TransitionLayer
fromCoords	first set of point locations (of SpatialPoints, matrix or numeric class)
toCoords	second, optional set of point locations (of SpatialPoints, matrix or numeric class)

Details

Cost units between cells are defined as the reciprocal of the values in the transition matrix.

The function uses Dijkstra's algorithm, as implemented in the igraph package.

A projection correction is needed for accuracy in the case of grid data for a longlat raster (see function geoCorrection).

Value

distance matrix (S3 class dist or matrix)

Author(s)

Jacob van Etten [e-mail]

References

E.W. Dijkstra. 1959. A note on two problems in connexion with graphs. Numerische Mathematik 1, 269-271.

See Also

accCost, geoCorrection

Examples

#create a new raster and set all its values to unity.
r <- raster(nrows=18, ncols=36) 
r <- setValues(r,runif(ncell(r),0,1))

#create a Transition object from the raster
tr <- transition(r,function(x) 1/mean(x),8)

#asymmetric
ncf <- function(x) max(x) - x[1] + x[2]
tr2 <- transition(r,ncf,8, symm=FALSE)

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

#from and to identical
costDistance(tr,sP1)
costDistance(tr2,sP1)

#from and to different
costDistance(tr,sP1,sP2)
costDistance(tr2,sP1,sP2)

gdistance documentation built on May 2, 2019, 5:46 p.m.