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SIEI (landscape level)

Source: R/lsm_l_siei.R
lsm_l_siei.Rd

Simpson's evenness index (Diversity metric)

Usage

lsm_l_siei(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

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

SIEI is a 'Diversity metric'. The metric is widely used in biodiversity and ecology. It is the ratio between the actual Simpson's diversity index and the theoretical maximum Simpson's diversity index.

Units

None

Range

0 < SIEI <= 1

Behaviour

Equals SIEI = 0 when only one patch is present and approaches SIEI = 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_siei(landscape)
#> # A tibble: 1 × 6
#>   layer level     class    id metric value
#>   <int> <chr>     <int> <int> <chr>  <dbl>
#> 1     1 landscape    NA    NA siei   0.906