Patch richness density (Diversity metric)
lsm_l_prd(landscape, directions = 8)tibble
Raster* Layer, Stack, Brick, SpatRaster (terra), stars, or a list of rasterLayers.
The number of directions in which patches should be connected: 4 (rook's case) or 8 (queen's case).
$$PRD = \frac{m} {A} * 10000 * 100 $$ where \(m\) is the number of classes and \(A\) is the total landscape area in square meters.
PRD is a 'Diversity metric'. It is one of the simplest diversity and composition measures.
In contrast to lsm_l_pr, it is a relative measure and following, comparable
among landscapes with different total landscape areas.
Number per 100 hectares
PR > 0
Approaches PRD > 1 when only one patch is present and the landscape is rather large. Increases, without limit, as the number of classes increases and the total landscape area decreases.
McGarigal, K., SA Cushman, and E Ene. 2012. FRAGSTATS v4: Spatial Pattern Analysis Program for Categorical and Continuous Maps. Computer software program produced by the authors at the University of Massachusetts, Amherst. Available at the following web site: https://www.umass.edu/landeco/