Shortest path

Calculates the shortest path from an origin to a goal

shortestPath(x, origin, goal, ...)

Arguments

x

TransitionLayer object

origin

SpatialPoints, vector or matrix with coordinates, at the moment only the first cell is taken into account

goal

SpatialPoints, vector or matrix with coordinates

...

Additional argument: output

Value

Transition object

Details

As an additional argument output, the desired output object can be specified: either “TransitionLayer” (default), “TransitionStack” or “SpatialLines”.

If there is more than one path either (1) transition values in the TransitionLayer get values of 1 / number of paths or (2) the SpatialLines object will contain more than one line.

See also

costDistance, accCost

Author

Jacob van Etten

Examples

#example equivalent to that in the documentation on r.cost/r.drain in GRASS
r <- raster(nrows=6, ncols=7, xmn=0, xmx=7, ymn=0, ymx=6, crs="+proj=utm +units=m")

r[] <- c(2, 2, 1, 1, 5, 5, 5,
         2, 2, 8, 8, 5, 2, 1,
         7, 1, 1, 8, 2, 2, 2,
         8, 7, 8, 8, 8, 8, 5,
         8, 8, 1, 1, 5, 3, 9,
         8, 1, 1, 2, 5, 3, 9)

tr <- transition(r, function(x) 1/mean(x), 8)
# 1/mean: reciprocal to get permeability
tr <- geoCorrection(tr)

c1 <- c(5.5,1.5)
c2 <- c(1.5,5.5)

#make a SpatialLines object for visualization
sPath1 <- shortestPath(tr, c1, c2, output="SpatialLines")
plot(r)
lines(sPath1)


#make a TransitionLayer for further calculations
sPath2 <- shortestPath(tr, c1, c2)

plot(raster(sPath2))