R/ch_volcano_raster.R

In CSHShydRology: Canadian Hydrological Analyses

#' Create Test Raster
#'
#' @description 
#' Creates a \pkg{raster} object of land surface elevations, as
#' used to test/demonstrate many functions requiring a digital elevation model 
#' (DEM). 
#' 
#' @details
#' No arguments are required as the DEM is created from the \pkg{base} 
#' \code{volcano} matrix of elevations.
#' 
#' @export 
#' @return Returns a raster object of land surface elevations. 
#' @author Dan Moore and Kevin Shook
#' @importFrom raster rasterFromXYZ crs
#' @importFrom magrittr %>%
#' @examples
#' test_raster <- ch_volcano_raster()
#' 
ch_volcano_raster <- function() {
  vol_mat <- datasets::volcano
  nr <- nrow(vol_mat)
  nc <- ncol(vol_mat)
  dx <- 10
  xmin <- 300481
  xmax <- xmin + (nc - 1)*dx
  ymin <- 5916112
  ymax <- ymin + (nr - 1)*dx
  x <- rep(seq(xmax, xmin, -dx), each = nr)
  y <- rep(seq(ymin, ymax, dx), times = nc)
  vol_ras <- data.frame(x, y, z = as.numeric(vol_mat)) %>%
    raster::rasterFromXYZ()
  raster::crs(vol_ras) <- "+proj=utm +zone=60 +south +datum=WGS84 +units=m +no_defs" 
  return(vol_ras)
}