# R/lsm_l_core_mn.R In landscapemetrics: Landscape Metrics for Categorical Map Patterns

#### Documented in lsm_l_core_mn

```#' CORE_MN (landscape level)
#'
#' @description Mean of core area (Core area metric)
#'
#' @param landscape Raster* Layer, Stack, Brick, SpatRaster (terra), stars, or a list of rasterLayers.
#' @param directions The number of directions in which patches should be
#' connected: 4 (rook's case) or 8 (queen's case).
#' @param consider_boundary Logical if cells that only neighbour the landscape
#' boundary should be considered as core
#' @param edge_depth Distance (in cells) a cell has the be away from the patch
#' edge to be considered as core cell
#'
#' @details
#' \deqn{CORE_{MN} = mean(CORE[patch_{ij}])}
#' where \eqn{CORE[patch_{ij}]} is the core area in square meters of each patch.
#'
#' CORE_MN is a 'Core area metric' and equals the mean of core areas of all patches
#' in the landscape. The core area is defined as all cells that have no
#' neighbour with a different value than themselves (rook's case).
#'
#' \subsection{Units}{Hectares}
#' \subsection{Range}{CORE_MN >= 0}
#' \subsection{Behaviour}{Equals CORE_MN = 0 if CORE = 0 for all patches. Increases,
#' without limit, as the core area indices increase.}
#'
#' @seealso
#'
#' @return tibble
#'
#' @examples
#' lsm_l_core_mn(landscape)
#'
#' @aliases lsm_l_core_mn
#' @rdname lsm_l_core_mn
#'
#' @references
#' 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: http://www.umass.edu/landeco/research/fragstats/fragstats.html
#'
#' @export
lsm_l_core_mn <- function(landscape,
directions = 8,
consider_boundary = FALSE,
edge_depth = 1) {
landscape <- landscape_as_list(landscape)

result <- lapply(X = landscape,
FUN = lsm_l_core_mn_calc,
directions = directions,
consider_boundary = consider_boundary,
edge_depth = edge_depth)

layer <- rep(seq_along(result),
vapply(result, nrow, FUN.VALUE = integer(1)))

result <- do.call(rbind, result)

}

lsm_l_core_mn_calc <- function(landscape, directions, consider_boundary, edge_depth, resolution = NULL){

core_patch <- lsm_p_core_calc(landscape,
directions = directions,
consider_boundary = consider_boundary,
edge_depth = edge_depth,
resolution = resolution)

# all values NA
if (all(is.na(core_patch\$value))) {
return(tibble::tibble(level = "landscape",
class = as.integer(NA),
id = as.integer(NA),
metric = "core_mn",
value = as.double(NA)))
}

core_mn <- mean(core_patch\$value)

return(tibble::tibble(level = "landscape",
class = as.integer(NA),
id = as.integer(NA),
metric = "core_mn",
value = as.double(core_mn)))
}
```

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landscapemetrics documentation built on Sept. 5, 2021, 5:20 p.m.