Perimeter-Area ratio (Shape 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).
Details
$$PARA = \frac{p_{ij}} {a_{ij}}$$ where \(p_{ij}\) is the perimeter in meters and \(a_{ij}\) is the area in square meters.
PARA is a 'Shape metric'. It describes the patch complexity in a straightforward way. However, because it is not standarised to a certain shape (e.g. a square), it is not scale independent, meaning that increasing the patch size while not changing the patch form will change the ratio.
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_para(landscape)
#> # A tibble: 28 × 6
#> layer level class id metric value
#> <int> <chr> <int> <int> <chr> <dbl>
#> 1 1 patch 1 1 para 4
#> 2 1 patch 1 2 para 2.4
#> 3 1 patch 1 3 para 0.833
#> 4 1 patch 1 4 para 4
#> 5 1 patch 1 5 para 4
#> 6 1 patch 1 6 para 0.85
#> 7 1 patch 1 7 para 1.38
#> 8 1 patch 1 8 para 3.33
#> 9 1 patch 1 9 para 2
#> 10 1 patch 2 10 para 1.12
#> # ℹ 18 more rows