PARA (patch level)

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.

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

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

See also

lsm_p_area, lsm_p_perim,
lsm_c_para_mn, lsm_c_para_sd, lsm_c_para_cv,
lsm_l_para_mn, lsm_l_para_sd, lsm_l_para_cv

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