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NDCA (landscape level)

Source: R/lsm_l_ndca.R
lsm_l_ndca.Rd

Number of disjunct core areas (Core area metric)

Usage

lsm_l_ndca(
  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

$$NDCA = \sum \limits_{i = 1}^{m} \sum \limits_{j = 1}^{n} n_{ij}^{core}$$ where \(n_{ij}^{core}\) is the number of disjunct core areas.

NDCA is a 'Core area metric'. The metric summarises the landscape as the sum of all patches in the landscape. A cell is defined as core if the cell has no neighbour with a different value than itself (rook's case). NDCA counts the disjunct core areas, whereby a core area is a 'patch within the patch' containing only core cells. It describes patch area and shape simultaneously (more core area when the patch is large, however, the shape must allow disjunct core areas). Thereby, a compact shape (e.g. a square) will contain less disjunct core areas than a more irregular patch.

Units

None

Range

NDCA >= 0

Behaviour

NDCA = 0 when TCA = 0, i.e. every cell in the landscape is an edge cell. NDCA increases, with out limit, as core area increases and patch shapes allow disjunct core areas (i.e. patch shapes become rather complex).

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_c_tca,
lsm_p_ncore, lsm_c_ndca

Examples

landscape <- terra::rast(landscapemetrics::landscape)
lsm_l_ndca(landscape)
#> # A tibble: 1 × 6
#>   layer level     class    id metric value
#>   <int> <chr>     <int> <int> <chr>  <dbl>
#> 1     1 landscape    NA    NA ndca      19