Skip to contents

Perimeter-Area ratio (Shape metric)

Usage

lsm_p_para(landscape, directions = 8)

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).

Value

tibble

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.

Units

None

Range

PARA > 0

Behaviour

Increases, without limit, as the shape complexity increases.

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