This function calculates the area of integer categories in a primary raster (r1). It can optionally compute an overlay area with a second layer (r2) and/or perform calculations within distinct zones defined by a polygon SpatVector.
Usage
area.calc.flex(
r1,
r2_raster = NULL,
r2_vector = NULL,
threshold = NULL,
zonal_polys = NULL,
id_col = NULL,
add_cols = NULL,
omit_zero = TRUE,
unit = "km"
)Arguments
- r1
The primary SpatRaster with integer categories.
- r2_raster
An optional SpatRaster for overlay analysis.
- r2_vector
An optional SpatVector for overlay analysis.
- threshold
A numeric value required to binarize 'r2_raster' if it's continuous.
- zonal_polys
An optional SpatVector for zonal analysis.
- id_col
A string specifying the column in 'zonal_polys'.
- add_cols
An optional character vector of additional column names from 'zonal_polys'.
- omit_zero
A logical value. If TRUE (default), results for category = 0 are removed.
- unit
A string specifying the area unit ("km", "m", or "ha").
Examples
# \donttest{
library(terra)
# Create land cover raster
# 1 = Forest, 2 = Grassland, 3 = Agriculture
land_cover <- rast(ncol = 30, nrow = 30,
xmin = -50, xmax = -49,
ymin = -15, ymax = -14,
crs = "EPSG:4326")
values(land_cover) <- sample(1:3, ncell(land_cover), replace = TRUE)
# Basic: Calculate area for each category
area_result <- area.calc.flex(land_cover, unit = "km")
#> Processing layer: lyr.1
# With zones: Calculate area by region
region1 <- vect("POLYGON ((-50 -15, -49.5 -15, -49.5 -14, -50 -14, -50 -15))",
crs = "EPSG:4326")
region2 <- vect("POLYGON ((-49.5 -15, -49 -15, -49 -14, -49.5 -14, -49.5 -15))",
crs = "EPSG:4326")
regions <- rbind(region1, region2)
regions$region_id <- c("A", "B")
area_zonal <- area.calc.flex(land_cover,
zonal_polys = regions,
id_col = "region_id",
unit = "km")
#> Processing layer: lyr.1
# With overlay: Calculate area within protected areas
protected <- rast(land_cover)
values(protected) <- sample(0:1, ncell(protected), replace = TRUE)
area_overlay <- area.calc.flex(land_cover,
r2_raster = protected,
unit = "km")
#> Preparing overlay layer...
#> Processing layer: lyr.1
# }