Interspersion and Juxtaposition index (Aggregation metric)
lsm_c_iji(landscape, verbose = TRUE)tibble
A categorical raster object: SpatRaster; Raster* Layer, Stack, Brick; stars or a list of SpatRasters.
Print warning message if not sufficient patches are present
$$IJI = \frac{- \sum \limits_{k = 1}^{m} \Bigg[ \Bigg( \frac{e_{ik}}{\sum \limits_{k = 1}^{m} e_{ik}} \Bigg) ln \Bigg( \frac{e_{ik}}{\sum \limits_{k = 1}^{m} e_{ik}} \Bigg) \Bigg]}{ln(m - 1)} * 100$$
where \(e_{ik}\) are the unique adjacencies of all classes (lower/upper triangle of the adjacency table - without the diagonal) and \(m\) is the number of classes.
IJI is an 'Aggregation metric'. It is a so called "salt and pepper" metric and describes the intermixing of classes (i.e. without considering like adjacencies - the diagonal of the adjacency table). The number of classes to calculate IJI must be >= than 3.
Percent
0 < IJI <= 100
Approaches 0 if a class is only adjacent to a single other class and equals 100 when a class is equally adjacent to all other classes.
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
McGarigal, K., & Marks, B. J. 1995. FRAGSTATS: spatial pattern analysis program for quantifying landscape structure. Gen. Tech. Rep. PNW-GTR-351. Portland, OR: US Department of Agriculture, Forest Service, Pacific Northwest Research Station. 122 p, 351.
lsm_l_iji
landscape <- terra::rast(landscapemetrics::landscape)
lsm_c_iji(landscape)
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