alternative function

it calculates alpha taxonomic diversity

NAMESPACE

@@ -3,6 +3,7 @@
 export(area.calc)
 export(load.data)
 export(spat.alpha)
+export(spat.alpha2)
 export(spat.beta)
 export(spat.rand)
 export(spat.trait)

R/alpha2.R

@@ -0,0 +1,30 @@
+#' Alternative method to calculate alpha taxonomic diversity
+#'
+#' @param bin A SpatRaster with presence-absence data (0 or 1) for
+#' a set of species.
+#' @param cores A positive integer. If cores > 1, a 'parallel'
+#' package cluster with that many cores is created and used.
+#' @param filename Character. Save results if a name is provided.
+#'
+#' @return A SpatRaster object with richness.
+#' @export
+#'
+#' @examples
+#' \donttest{
+#' library(terra)
+#' bin1 <- terra::rast(system.file("extdata", "ref.tif",
+#' package = "divraster"))
+#' spat.alpha2(bin1)
+#' }
+spat.alpha2 <- function(bin, cores = 1, filename = "") {
+  res <- terra::app(bin, sum, na.rm = TRUE)
+  names(res) <- "Richness"
+
+  if (filename != "") {
+    terra::writeRaster(res,
+                       filename = filename,
+                       overwrite = TRUE)
+  }
+
+  return(res)
+}