landscapemetrics (version 1.4.4)

get_patches: get_patches

Description

Connected components labeling to derive patches in a landscape.

Usage

get_patches(landscape, class, directions, to_disk, return_raster)
# S3 method for RasterLayer
get_patches(
  landscape,
  class = "all",
  directions = 8,
  to_disk = getOption("to_disk", default = FALSE),
  return_raster = TRUE
)
# S3 method for RasterStack
get_patches(
  landscape,
  class = "all",
  directions = 8,
  to_disk = getOption("to_disk", default = FALSE),
  return_raster = TRUE
)
# S3 method for RasterBrick
get_patches(
  landscape,
  class = "all",
  directions = 8,
  to_disk = getOption("to_disk", default = FALSE),
  return_raster = TRUE
)
# S3 method for stars
get_patches(
  landscape,
  class = "all",
  directions = 8,
  to_disk = getOption("to_disk", default = FALSE),
  return_raster = TRUE
)
# S3 method for list
get_patches(
  landscape,
  class = "all",
  directions = 8,
  to_disk = getOption("to_disk", default = FALSE),
  return_raster = TRUE
)
# S3 method for matrix
get_patches(
  landscape,
  class = "all",
  directions = 8,
  to_disk = getOption("to_disk", default = FALSE),
  return_raster = FALSE
)

Arguments

landscape

Raster* Layer, Stack, Brick or a list of rasterLayers.

class

Either "all" (default) for every class in the raster, or specify class value. See Details.

directions

The number of directions in which patches should be connected: 4 (rook's case) or 8 (queen's case).

to_disk

Logical argument, if FALSE results of get_patches are hold in memory. If true, get_patches writes temporary files and hence, does not hold everything in memory. Can be set with a global option, e.g. option(to_disk = TRUE). See Details.

return_raster

If false, matrix is returned

Value

List

Details

Searches for connected patches (neighbouring cells of the same class i). The 8-neighbours rule ('queen's case) or 4-neighbours rule (rook's case) is used. Returns a list with raster. For each class the connected patches have the value 1 - n. All cells not belonging to the class are NA.

Landscape metrics rely on the delineation of patches. Hence, get_patches is heavily used in landscapemetrics. As raster can be quite big, the fact that get_patches creates a copy of the raster for each class in a landscape becomes a burden for computer memory. Hence, the argument to_disk allows to store the results of the connected labeling algorithm on disk. Furthermore, this option can be set globally, so that every function that internally uses get_patches can make use of that.

References

Vincent, L., Soille, P. 1991. Watersheds in digital spaces: an efficient algorithm based on immersion simulations. IEEE Transactions on Pattern Analysis and Machine Intelligence. 13 (6), 583-598

Examples

# NOT RUN {
# check for patches of class 1
patched_raster <- get_patches(landscape, class = 1)

# count patches
length(raster::unique(patched_raster[[1]]))

# check for patches of every class
patched_raster <-  get_patches(landscape)

# }