Standard deviation 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
$$PARA_{SD} = sd(PARA[patch_{ij}]$$ where \(PARA[patch_{ij}]\) is the perimeter area ratio of each patch.
PARA_SD is a 'Shape metric'. It summarises the landscape as the standard deviation of each patch belonging in the landscape. The perimeter-area ratio 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