R/tesselate.R

In lawn: Client for 'Turfjs' for 'Geospatial' Analysis

#' Tesselate
#'
#' Tesselates a [data-Polygon] into a
#' [data-FeatureCollection] of
#' triangles using earcut (github.com/mapbox/earcut)
#'
#' @export
#' @param polygon Input [data-Feature]<([data-Polygon])>
#' @template lint
#' @family assertions
#' @return A [data-FeatureCollection]
#' @examples
#' poly <- '{
#'  "type": "Feature",
#'   "properties": {
#'     "fill": "#0f0"
#'   },
#'   "geometry": {
#'     "type": "Polygon",
#'     "coordinates": [[
#'       [-46.738586, -23.596711],
#'       [-46.738586, -23.458207],
#'       [-46.560058, -23.458207],
#'       [-46.560058, -23.596711],
#'       [-46.738586, -23.596711]
#'     ]]
#'   }
#' }'
#' lawn_tesselate(poly)
#'
#' xx <- jsonlite::fromJSON(lawn_data$polygons_within, FALSE)
#' lawn_tesselate(xx$features[[1]])
#' @examples \dontrun{
#' lawn_tesselate(xx$features[[1]]) %>% view
#' lawn_tesselate(poly) %>% view
#' }
lawn_tesselate <- function(polygon, lint = FALSE) {
  poly <- convert(polygon)
  lawnlint(poly, lint)
  if (lint) is_type(polygon, "Feature", "Polygon")
  ct$eval(sprintf("var er = turf.tesselate(%s);", poly))
  tmp <- ct$get("er")
  structure(tmp, class = tolower(tmp$type))
}