overlap_null_distrib {BoundaryStats}

Null distribution for boundary overlap statistics

Description

Creates custom probability distributions for three boundary overlap statistics (directly overlapping boundary elements, minimum distance between boundary elements in x to y, and minimum distance between elements in x and y). Given two SpatRaster objects with the same extent, projection, and resolution, simulates n iterations of random raster surfaces from neutral model(s).

Usage

overlap_null_distrib(
  x,
  y,
  rand_both,
  x_convert = FALSE,
  y_convert = FALSE,
  x_cat = FALSE,
  y_cat = FALSE,
  threshold = 0.2,
  n_iterations = 10,
  x_model = "random",
  y_model = "random",
  px = 0.5,
  py = 0.5,
  progress = TRUE
)

Arguments

x

A SpatRaster object. If rand_both = FALSE, only this raster will be modeled.

y

A SpatRaster object. If rand_both = FALSE, this raster does not change.

rand_both

TRUE if distribution of traits in x and y should be modeled.

x_convert

TRUE if x contains numeric trait data that needs to be converted to boundary intensities. default = FALSE.

y_convert

TRUE if y contains numeric trait data that needs to be converted to boundary intensities. default = FALSE.

x_cat

TRUE if x contains a categorical variable. default = FALSE.

y_cat

TRUE if y contains a categorical variable. default = FALSE.

threshold

A value between 0 and 1. The proportion of cells to keep as boundary elements. Default = 0.2.

n_iterations

An integer indicating the number of iterations for the function. A value of 100 or 1000 is recommended to produce sufficient resolution for downstream statistical tests. default = 10.

x_model

Neutral model to use. Options: 'random' (stochastic), 'gaussian' (Gaussian random field), and 'random_cluster' (modified random clusters method)

y_model

Neutral model to use for y.

px

If using modified random clusters for x, proportion of cells to be marked in percolated raster. Higher values of p produce larger clusters. Default = 0.5

py

If using modified random clusters for y, proportion of cells to be marked in percolated raster. Higher values of p produce larger clusters. Default = 0.5

progress

If progress = TRUE (default) a progress bar will be displayed.

Value

A list of probability distribution functions for boundary overlap statistics.

Author(s)

Amy Luo

References

Saura, S. & Martínez-Millán, J. (2000). Landscape patterns simulation with a modified random clusters method. Landscape Ecology, 15:661-678.

Examples

data(T.cristatus)
T.cristatus <- terra::rast(T.cristatus_matrix, crs = T.cristatus_crs)
terra::ext(T.cristatus) <- T.cristatus_ext

data(grassland)
grassland <- terra::rast(grassland_matrix, crs = grassland_crs)
terra::ext(grassland) <- grassland_ext

Tcrist_ovlp_null <- overlap_null_distrib(T.cristatus, grassland, rand_both = FALSE,
  x_cat = TRUE, n_iterations = 100, x_model = 'random_cluster')