CAI (patch level)

Core area index (Core area metric)

Usage

lsm_p_cai(landscape, directions = 8, consider_boundary = FALSE, edge_depth = 1)

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

Value

tibble

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.

Because the metric is based on distances or areas please make sure your data is valid using check_landscape.

Units

Percent

Range

0 <= CAI <= 100

Behaviour

CAI = 0 when the patch has no core area and approaches CAI = 100 with increasing percentage of core area within a patch.

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

See also

lsm_p_core, lsm_p_area,
lsm_c_cai_mn, lsm_c_cai_sd, lsm_c_cai_cv, lsm_c_cpland,
lsm_l_cai_mn, lsm_l_cai_sd, lsm_l_cai_cv

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