R/pastclim_rast.R

In pastclim: Manipulate Time Series of Climate Reconstructions

#' Read a raster for pastclim
#'
#' This function is a wrapper around [terra::rast()], with additional logic to
#' correctly import time for vrt datasets (time is stored as custom metadata in
#' pastclim-generated vrt files)
#' @param x filename of the raster
#' @param bio_var_orig the variable name as present in the file
#' @param bio_var_pastclim the variable name as used by pastclim (thus allowing
#'   us to rename the variable)
#' @returns a [`terra::SpatRaster`]
#'
#' @keywords internal
pastclim_rast <- function(x, bio_var_orig, bio_var_pastclim,
                          var_longname = NULL, var_units = NULL) {
  # if we have an nc file
  if (substr(x, nchar(x) - 2, nchar(x)) != "vrt") {
    var_rast <- terra::rast(x, subds = bio_var_orig)
    time_vector <- time_bp(var_rast)
    time_bp_display <- TRUE
    ## TODO we should really add an attribute to nc files to determine whether
    ## we want to label with time bp or time ce. Ideally, the same as what we
    ## use for vrt with `pastclim_time_bp`
  } else { # if we have a vrt file
    # check that the variable name is as expected
    vrt_meta <- vrt_get_meta(x)
    if (vrt_meta$description != bio_var_orig) {
      stop(
        "the file ", x, " does not include the expected variable ",
        bio_var_orig
      )
    }
    time_vector <- vrt_meta$time_bp
    var_rast <- terra::rast(x)
    time_bp(var_rast) <- time_vector
    time_bp_display <- vrt_meta$time_bp_display
  }
  # set the varnames and names for the raster
  varnames(var_rast) <- bio_var_pastclim
  # for names, we append time, either as bp or as ce
  if (time_bp_display) {
    names(var_rast) <- paste(bio_var_pastclim, time_vector, sep = "_")
  } else {
    names(var_rast) <- paste(bio_var_pastclim, time_vector + 1950, sep = "_")
  }
  if (!is.null(var_longname)) {
    longnames(var_rast) <- var_longname
  }
  if (!is.null(var_units)) {
    units(var_rast) <- var_units
  }
  return(var_rast)
}