R/create_grid.R

In riatelab/potential: Implementation of the Potential Model

#' @title Create a Regularly Spaced Points Grid
#' @name create_grid
#' @description This function creates a regular grid of points
#' from the extent of a given spatial object and a given resolution.
#' @param x an sf or sfc object, the spatial extent of this object is used to
#' create the regular grid.
#' @param res resolution of the grid (in map units).
#' @return The output of the function is an sf object of regularly spaced
#' points with the extent of x.
#' @examples
#' library(sf)
#' g <- create_grid(x = n3_poly, res = 200000)
#' plot(st_geometry(g))
#' plot(st_geometry(n3_poly), border = "red", add = TRUE)
#' @importFrom sf st_as_sf st_crs st_bbox
#' @export
create_grid <- function(x, res) {
  
  if (!inherits(x = x, what = c("sfc", "sf"))) {
    stop("x is not an sf or an sfc object.", 
         call. = FALSE)
  }
  

  bb <- st_bbox(x)
  rounder <- bb %% res
  bb[1:2] <- bb[1:2] - rounder[1:2]
  bb[3:4] <- bb[3:4] + res - rounder[3:4]
  cx <- seq(from = bb[1], to = bb[3], by = res)
  cy <- seq(from = bb[2], to = bb[4], by = res)
  
  g <- expand.grid(cx, cy)
  g <- data.frame(
    ID = 1:nrow(g),
    COORDX = g[, 1],
    COORDY = g[, 2]
  )
  g <- st_as_sf(g,
                coords = c("COORDX", "COORDY"),
                crs = st_crs(x), remove = FALSE
  )
  
  return(g)
}