R/addVertices.R

In openfigis/RFigisGeo: Set of geoprocessing facilities used in FIGIS

#' @name addVertices
#' @title addVertices
#' @description Densify a spatial polygon by adding vertices
#' 
#' @param sp an object of class "SpatialPolygons"
#' @param each the step value to use to create vertices
#' @param parallel run in parallel
#' @param ... parallel options
#' @return an object of class "SpatialPolygons"
#' 
#' @author Emmanuel Blondel \email{emmanuel.blondel1@@gmail.com}
#'
addVertices <- function(sp, each = 0.1, parallel = FALSE, ...){
  
  applyHandler <- if(parallel) parallel::mclapply else lapply
  
  sp@polygons <- applyHandler(sp@polygons, function(p){
    coords <- slot(p,"Polygons")[[1]]@coords
    newcoords <- do.call("rbind",lapply(1:(nrow(coords)-1), function(i){
      i_coords <- coords[i:(i+1),]
      out_coords <- data.frame(
        x = seq(from = i_coords[1L,1L], to = i_coords[2L,1L],
                by = ifelse(i_coords[1L,1L]<=i_coords[2L,1L], each, -each)),
        y = seq(from = i_coords[1L,2L], to = i_coords[2L,2L],
                by = ifelse(i_coords[1L,2L]<=i_coords[2L,2L], each, -each))
      )
      if(i<(nrow(coords)-1)) out_coords <- out_coords[,-nrow(out_coords)]
      out_coords <- as.matrix(out_coords)
      return(out_coords)
    }))
    slot(p,"Polygons")[[1]]@coords <- newcoords
    return(p)
  }, ...)
  return(sp)
}