distref.raster: Transfrom reference raster as a network of paths for distance...
In statnmap/GeoDist: Constrained distance calculation and associated geotools

Description Usage Arguments Details Value

View source: R/Calculate_distances_functions.R

Transfrom reference raster as a network of paths for distance calculation

distref.raster(
  r.ref,
  step.ang = 5,
  filename = paste0(tempdir(), "/dref.r.RData"),
  r.ref3D = FALSE,
  n.cores,
  save.rdists
)

`r.ref`	Raster (1-layer) that will be used to calculate distances. Its resolution impacts precision on distances.
`step.ang`	Step for angles classes breaks (in degrees). This means that a distance error is allowed in future calculations. Distance error (%) = 100 * (1 - cos((step.ang/2)*pi/180)). With step.ang = 5 degrees, error < 0.1%. Default set to 5.
`filename`	Path where to save the dref.r issued from reference raster. This may be usefull for re-using the raster for different datasets. Default to paste0(tempdir(), "/dref.r.RData")
`r.ref3D`	Logical. Wether the reference raster should be used as a 3D surface to calculate distance accounting for elevation.
`n.cores`	number of cores to run parallel calculation. Default to all cores using parallel::detectCores()
`save.rdists`	optional. Path to file where to save the distances matrix between all non-NA raster cells. Saved as csv. If not provided, distances matrix will not be calculated as it may be to big to be stored in memory.

Not all direct possible paths are calculated. Direct paths are retained in a focal window around cells. The size of the focal window is determined by the step.ang value. All paths retained are stored in a undirected graph (as from library igraph). All paths real distances are also stored to be weights for future points to points distances calculations.

coords.r coordinates of all cells of the raster r.ref.NA.nb cell that are NA in the reference raster (obstacles) cell.Relpos.ngb row and col of neighbors retained after the angle calculation, relative to the cell of origin (moving window) cell.Relpos.cross row and col of cells crossed by lines between origin and neighbors, relative to the cell of origin (moving window)

statnmap/GeoDist documentation built on Feb. 4, 2020, 8:34 p.m.