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SIDI (landscape level)

Source: R/lsm_l_sidi.R
lsm_l_sidi.Rd

Simpson's diversity index (Diversity metric)

Usage

lsm_l_sidi(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

$$SIDI = 1 - \sum \limits_{i = 1}^{m} P_{i}^{2}$$ where \(P_{i}\) is the proportion of class i and \(m\) is the number of classes.

SIDI is a 'Diversity metric'. It is widely used in biodiversity and ecology. It is less sensitive to rare class types than lsm_l_shdi. It can be interpreted as the probability that two randomly selected cells belong to the same class.

Units

None

Range

0 <= SIDI < 1

Behaviour

Equals SIDI = 0 when only one patch is present and approaches SIDI < 1 when the number of class types increases while the proportions are equally distributed

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

Simpson, E. H. 1949. Measurement of diversity. Nature 163:688

See also

lsm_c_pland, lsm_l_pr

Examples

landscape <- terra::rast(landscapemetrics::landscape)
lsm_l_sidi(landscape)
#> # A tibble: 1 × 6
#>   layer level     class    id metric value
#>   <int> <chr>     <int> <int> <chr>  <dbl>
#> 1     1 landscape    NA    NA sidi   0.604