closestdist_gcms: Distance between General Circulation Models (GCMs)

In chooseGCM: Selecting General Circulation Models for Species Distribution Modeling

Distance between General Circulation Models (GCMs)

Description

This function compares future climate projections from multiple General Circulation Models (GCMs) based on their similarity in terms of bioclimatic variables. It computes distance metrics between GCMs and identifies subsets of GCMs that are similar to the global set.

Usage

closestdist_gcms(
  s,
  var_names = c("bio_1", "bio_12"),
  study_area = NULL,
  scale = TRUE,
  k = NULL,
  method = "euclidean",
  minimize_difference = TRUE,
  max_difference = NULL
)

Arguments

s	A list of stacks of General Circulation Models (GCMs).
var_names	Character. A vector with names of the bioclimatic variables to compare, or 'all' to include all available variables.
study_area	An Extent object, or any object from which an Extent object can be extracted. Defines the study area for cropping and masking the rasters.
scale	Logical. Whether to apply centering and scaling to the data. Default is TRUE.
k	Numeric. The number of GCMs to include in the subset. If NULL (default), stopping criteria are applied.
method	The distance method to use. Default is "euclidean". Possible values are: "euclidean", "maximum", "manhattan", "canberra", "binary", "minkowski", "pearson", "spearman", or "kendall". See ?dist_gcms.
minimize_difference	Logical. If k = NULL, the function will search for the optimal value of k by adding GCMs to the subset until the mean distance starts to diverge from the global mean distance. Default is TRUE.
max_difference	Numeric. A distance threshold to stop searching for the optimal subset. If NULL, no threshold is set. Default is NULL.

Details

The minimize_difference option searches for the best value of k by progressively adding GCMs to the subset. The function monitors the mean distance between the subset of GCMs and the global mean distance, stopping when the distance begins to increase. The max_difference option sets a maximum distance difference. If the mean distance between the subset GCMs exceeds this threshold, the function stops searching and returns the current subset.

Value

A set of GCMs that have a mean distance closer to the global mean distance of all GCMs provided in s.

Author(s)

Luíz Fernando Esser ([e-mail]) https://luizfesser.wordpress.com

See Also

cor_gcms dist_gcms

Examples

var_names <- c("bio_1", "bio_12")
s <- import_gcms(system.file("extdata", package = "chooseGCM"), var_names = var_names)
study_area <- terra::ext(c(-80, -30, -50, 10)) |> terra::vect(crs="epsg:4326")
closestdist_gcms(s, var_names, study_area, method = "euclidean")

chooseGCM documentation built on April 3, 2025, 5:27 p.m.