R/retrieve_raster.R

In apear9/rdwplus: Inverse Distance Weighted Percent Land Use for Streams

#' Write a raster layer from the current GRASS mapset to file
#' @description This function writes a GRASS mapset raster to file.
#' @param layer The name of the raster in the GRASS mapset that is to be written out.
#' @param out_layer The name of the file to be created, with the relevant file extension.
#' @param overwrite A logical indicating whether the output from this function should be allowed to overwrite any existing files. Defaults to \code{FALSE}.
#' @param ... Additional arguments to \code{r.out.gdal}.
#' @return Nothing.
#' @examples
#' # Will only run if GRASS is running
#' if(check_running()){
#' 
#' # Load data set
#' dem <- system.file("extdata", "dem.tif", package = "rdwplus")
#' 
#' # Set environment parameters and import data to GRASS
#' set_envir(dem)
#' raster_to_mapset(rasters = dem, as_integer = FALSE)
#' 
#' # Retrieve raster 
#' out_name <- paste0(tempdir(), "/retrieved_dem.tif")
#' retrieve_raster("dem.tif", out_layer = out_name, overwrite = TRUE)
#' 
#' }
#' @export
retrieve_raster <- function(layer, out_layer, overwrite = FALSE, ...){
  
  # Check that GRASS is running
  if(!check_running()) stop("There is no valid GRASS session. Program halted.")
  
  # Check that both input lengths the same
  n_layers <- length(layer)
  n_outs   <- length(out_layer)
  if(n_layers != n_outs) stop("Number of inputs and outputs must be the same.")
  
  # Set flags
  flags <- c("quiet", "c")
  if(overwrite) flags <- c(flags, "overwrite")
  
  # Create extra 
  
  # Loop over in/out
  for(i in 1:n_layers){
    execGRASS(
      'r.out.gdal', 
      flags = c("overwrite", "quiet", "c"),
      parameters = list(
        input = layer[i],
        output = out_layer[i],
        ...
      )
    )
  }
  
  # Return nothing
  invisible()
  
}