Skip to contents

Core area index (Core area metric)

Usage

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

Arguments

landscape

Raster* Layer, Stack, Brick, SpatRaster (terra), stars, or a list of rasterLayers.

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.

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. 2012. FRAGSTATS v4: Spatial Pattern Analysis Program for Categorical and Continuous Maps. Computer software program produced by the authors at the University of Massachusetts, Amherst. Available at the following web site: http://www.umass.edu/landeco/research/fragstats/fragstats.html

Examples

lsm_p_cai(landscape)
#> # A tibble: 27 × 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     48.0
#>  4     1 patch     1     4 cai      0  
#>  5     1 patch     1     5 cai      0  
#>  6     1 patch     1     6 cai     14.3
#>  7     1 patch     1     7 cai      0  
#>  8     1 patch     1     8 cai      0  
#>  9     1 patch     1     9 cai      0  
#> 10     1 patch     2    10 cai     31.4
#> # … with 17 more rows