import(Matrix) 
import(igraph)
importClassesFrom(sp, SpatialPoints, SpatialPointsDataFrame,
SpatialPixels, SpatialGrid, SpatialPixelsDataFrame, SpatialGridDataFrame)
importClassesFrom(raster, BasicRaster, Raster)
importFrom(raster, nlayers, stack, raster)

importFrom(methods, Ops, Arith, Compare, Logic)
exportClasses(TransitionLayer, TransitionStack, Coords)
exportPattern("^[^\\.]")
exportMethods(initialize, show, coerce, Ops, Arith, Compare, Logic, "[", "[<-", accCost, costDistance, geoCorrection, normalize, pathInc, passage, transition, resistanceDistance, shortestPath)