#' LPI (landscape level)
#'
#' @description Largest patch index (Area and Edge metric)
#'
#' @param landscape A categorical raster object: SpatRaster; Raster* Layer, Stack, Brick; stars or a list of SpatRasters.
#' @param directions The number of directions in which patches should be
#' connected: 4 (rook's case) or 8 (queen's case).
#'
#' @details
#' \deqn{LPI = \frac{\max (a_{ij})} {A} * 100}
#' where \eqn{max(a_{ij})} is the area of the patch in square meters and \eqn{A}
#' is the total landscape area in square meters.
#'
#' The largest patch index is an 'Area and edge metric'. It is the percentage of the
#' landscape covered by the largest patch in the landscape. It is a simple
#' measure of dominance.
#'
#' Because the metric is based on distances or areas please make sure your data
#' is valid using \code{\link{check_landscape}}.
#'
#' \subsection{Units}{Percentage}
#' \subsection{Range}{0 < LPI <= 100}
#' \subsection{Behaviour}{Approaches LPI = 0 when the largest patch is becoming small
#' and equals LPI = 100 when only one patch is present}
#'
#' @seealso
#' \code{\link{lsm_p_area}},
#' \code{\link{lsm_l_ta}}, \cr
#' \code{\link{lsm_c_lpi}}
#'
#' @return tibble
#'
#' @examples
#' landscape <- terra::rast(landscapemetrics::landscape)
#' lsm_l_lpi(landscape)
#'
#' @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
#'
#' @export
lsm_l_lpi <- function(landscape, directions = 8) {
landscape <- landscape_as_list(landscape)
result <- lapply(X = landscape,
FUN = lsm_l_lpi_calc,
directions = directions)
layer <- rep(seq_along(result),
vapply(result, nrow, FUN.VALUE = integer(1)))
result <- do.call(rbind, result)
tibble::add_column(result, layer, .before = TRUE)
}
lsm_l_lpi_calc <- function(landscape, directions, resolution, extras = NULL) {
# get patch area
patch_area <- lsm_p_area_calc(landscape,
directions = directions,
resolution = resolution,
extras = extras)
# summarise to total area
total_area <- sum(patch_area$value)
# all values NA
if (is.na(total_area)) {
return(tibble::new_tibble(list(level = "landscape",
class = as.integer(NA),
id = as.integer(NA),
metric = "lpi",
value = as.double(NA))))
}
# maximum value of patch_area / total_area
lpi <- max(patch_area$value / total_area * 100)
return(tibble::new_tibble(list(level = rep("landscape", length(lpi)),
class = rep(as.integer(NA), length(lpi)),
id = rep(as.integer(NA), length(lpi)),
metric = rep("lpi", length(lpi)),
value = as.double(lpi))))
}
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.