sample_raster: Sample points or patches on a categorical raster layer
In graph4lg: Build Graphs for Landscape Genetics Analysis

sample_raster

R Documentation

Sample points or patches on a categorical raster layer

Description

The function samples points or patches on a categorical raster layer.

Usage

sample_raster(
  raster,
  class,
  nb_pts,
  dist_min = 0,
  edge_size = 0,
  by_patch = TRUE,
  neighborhood = 8,
  surf_min = 0,
  prop_area = TRUE,
  step_max = 1000,
  output = "df",
  desc = TRUE
)

Arguments

`raster`	A RasterLayer object corresponding to a categorical raster layer
`class`	An integer value or vector with the value(s) corresponding to the code values of the raster layer within which points will be sampled.
`nb_pts`	An integer value indicating the number of points to be sampled
`dist_min`	An integer value indicating the minimum distance separating the sampled points (default = 0).
`edge_size`	An integer value indicating the width of the edge of the raster layer which is ignored during the sampling (default = 0). It prevents from sampling in the margins of the study area.
`by_patch`	A logical value indicating whether contiguous patches with cells having the same code value are delineated prior to sampling (default = TRUE). It prevents from sampling several points in the same contiguous patch.
`neighborhood`	An integer value indicating which cells are considered adjacent when contiguous patches are delineated (it should be 8 (default, Queen's case) or 4 (Rook's case)). This parameter is ignored when `by_patch = FALSE`.
`surf_min`	An integer value indicating the minimum surface of a patch considered for the sampling in number of raster cells. This parameter is used whatever the `by_patch` argument is. Default is 0.
`prop_area`	A logical value indicating whether sampling in large patches is more likely (default = TRUE). If `by_patch = FALSE`, this parameter is ignored. When `prop_area = TRUE`, the probability to sample a given patch is proportional to its area.
`step_max`	An integer value indicating how many sampling steps are performed to identify a point set satisfying all the conditions before returning an error.
`output`	A character string indicating the type of returned output: 'data.frame': A `data.frame` with three/four columns: ID: The point or patch centroid ID x: The point or patch centroid longitude y: The point or patch centroid latitude area: The area of the sampled patch (only if `by_patch = TRUE`) 'pts_layer': A `SpatialPointsDataFrame` layer corresponding to the sampled point (points or patch centroids) 'poly_layer': A `SpatialPolygonsDataFrame` layer corresponding to the sampled patch polygons
`desc`	A logical value indicating whether the result should be described or not (default = FALSE). If `desc = TRUE`, then the Gini coefficient of the distances between points and of the patch areas (if `by_patch = TRUE`) is computed with the `gini_coeff`. An histogram of the link weights is also described.