Core area index (Core area metric)
Arguments
- landscape
A categorical raster object: SpatRaster; Raster* Layer, Stack, Brick; stars or a list of SpatRasters.
- directions
The number of directions in which patches should be connected: 4 (rook's case) or 8 (queen's case).
- consider_boundary
Logical if cells that only neighbour the landscape boundary should be considered as core
- edge_depth
Distance (in cells) a cell has the be away from the patch edge to be considered as core cell
Details
$$CAI = (\frac{a_{ij}^{core}} {a_{ij}}) * 100$$ where \(a_{ij}^{core}\) is the core area in square meters and \(a_{ij}\) is the area in square meters.
CAI is a 'Core area metric'. It equals the percentage of a patch that is core area. A cell is defined as core area if the cell has no neighbour with a different value than itself (rook's case). It describes patch area and shape simultaneously (more core area when the patch is large and the shape is rather compact, i.e. a square). Because the index is relative, it is comparable among patches with different area.
References
McGarigal K., SA Cushman, and E Ene. 2023. FRAGSTATS v4: Spatial Pattern Analysis Program for Categorical Maps. Computer software program produced by the authors; available at the following web site: https://www.fragstats.org
Examples
landscape <- terra::rast(landscapemetrics::landscape)
lsm_p_cai(landscape)
#> # A tibble: 28 × 6
#> layer level class id metric value
#> <int> <chr> <int> <int> <chr> <dbl>
#> 1 1 patch 1 1 cai 0
#> 2 1 patch 1 2 cai 0
#> 3 1 patch 1 3 cai 48.6
#> 4 1 patch 1 4 cai 0
#> 5 1 patch 1 5 cai 0
#> 6 1 patch 1 6 cai 47.5
#> 7 1 patch 1 7 cai 18.7
#> 8 1 patch 1 8 cai 0
#> 9 1 patch 1 9 cai 0
#> 10 1 patch 2 10 cai 26.5
#> # ℹ 18 more rows