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Calculate SpatRaster Layer Areas and Overlap Areas

Source: R/range_size.R
area.calc.Rd

Calculates the total area for each layer (e.g., species) within a SpatRaster object. Optionally, it can also compute the overlapping areas between the primary SpatRaster (x) and one or two additional single-layer SpatRaster objects (y and z). Results are returned as a data.frame and can optionally be saved to a CSV file.

Usage

area.calc(x, y = NULL, z = NULL, filename = "", unit = "km", cellsize = NULL)

Arguments

x

A SpatRaster object for which the area of each layer will be calculated. This SpatRaster can have one or multiple layers.

y

An optional SpatRaster object with a single layer. If provided, the overlapping area between each layer in x and this y raster will be calculated. It should have the same extent and resolution as x.

z

An optional SpatRaster object with a single layer. If provided, the overlapping area between each layer in x and this z raster, as well as the three-way overlap (x, y, and z), will be calculated. Requires y to also be provided. It should have the same extent and resolution as x.

filename

Character string. If provided (e.g., "results.csv"), the resulting data frame will be saved to a CSV file with this name. If not provided, results are returned only to the R session.

unit

Character string specifying the unit of measurement for area calculations. Defaults to "km" (kilometers). Other options include "ha" (hectares), "m" (meters), etc.

cellsize

Numeric. An optional value specifying the cell size (area of a single cell) to be used for calculations. If NULL (default), the function will automatically determine the cell size from the input raster x.

Value

A data.frame with the following columns:

  • Layer: Name of each layer from the input SpatRaster x.

  • Area: The calculated area for each layer in x (e.g., total species range area).

  • Overlap_Area_Y (optional): If y is provided, the area where the x layer and y raster both have a value of 1 (overlap).

  • Overlap_Area_Z (optional): If z is provided, the area where the x layer and z raster both have a value of 1 (overlap).

  • Overlap_Area_All (optional): If both y and z are provided, the area where the x layer, y raster, and z raster all have a value of 1 (triple overlap).

Areas are reported in the specified unit.

Examples

# \donttest{
library(terra)
#> terra 1.8.70

# Load example rasters for demonstration
# Ensure these files are present in your package's inst/extdata folder
bin_rast <- terra::rast(system.file("extdata", "ref.tif", package = "divraster"))

# Example 1: Calculate area for 'bin_rast' only
area_only <- area.calc(bin_rast)
area_only
#>    Layer     Area
#> 1      A 6153.736
#> 2      B 6346.040
#> 3      C 4615.302
#> 4      D 5961.431
#> 5      E 6153.736
#> 6      F 5384.519
#> 7      G 5384.519
#> 8      H 5192.214
#> 9      I 6346.040
#> 10     J 6153.736
# }