R/vrt_set_meta.R

In pastclim: Manipulate Time Series of Climate Reconstructions

####################### ' Set vrt metadata ' ' This function sets the metadata
# information to a vrt file. It creates some dataset ' wide metadata, as well as
# band specific descriptions and times. ' @param vrt_path path to the XML file
# defining the vrt dataset ' @param description a string with the description of
# the variable in this dataset ' @param time_vector a vector of descriptions
# (same length as the number of bands) ' @param time_bp boolean defining whether
# time is in BP or (if FALSE) CE ' @returns TRUE if the file was updated
# correctly, FALSE if the update failed ' ' @keywords internal # Edit the vrt
# metadata
vrt_set_meta <- function(vrt_path, description, time_vector, time_bp = TRUE) {
  # read vrt file
  x <- xml2::read_xml(vrt_path)
  # TODO ideally we should check that we don't already have metadata to avoid
  # writing it twice check that we don't alreayd have metadata information
  # needed for pastclim
  has_time_node <-
    xml2::xml_find_first(x, "./Metadata/MDI[@key = 'pastclim_time_bp']")
  if (!inherits(has_time_node, "xml_missing")) {
    warning("metadata for pastclim is already present in ", vrt_path)
    return(FALSE)
  }
  # add metadata to indicate that we have a time axis
  xml2::xml_add_child(x, "Description", description, .where = 0)
  xml2::xml_add_child(x, "Metadata", .where = 1)
  metadata_node <- xml2::xml_find_first(x, xpath = "Metadata")
  xml2::xml_add_child(metadata_node, "MDI",
    key = "pastclim_time_bp",
    tolower(as.character(time_bp))
  )
  # add band description and times
  band_nodes <- xml2::xml_find_all(x, xpath = "VRTRasterBand")
  if (length(band_nodes) != length(time_vector)) {
    warning(
      "the vrt ", vrt_path,
      " has a different number of bands from the ",
      "length of the time vector"
    )
    return(FALSE)
  }
  for (i_node in seq_len(length(band_nodes))) {
    # add a unique description label for this band (variable_time combination)
    xml2::xml_add_child(band_nodes[i_node], "Description",
      paste(description, time_vector[i_node], sep = "_"),
      .where = 0
    )
    # add time for this band
    xml2::xml_add_child(band_nodes[i_node], "Metadata", .where = 1)
    metadata_node <- xml2::xml_find_first(band_nodes[i_node],
      xpath = "Metadata"
    )
    xml2::xml_add_child(metadata_node, "MDI",
      key = "time",
      time_vector[i_node]
    )
  }
  # overwrite vrt file with the new version
  xml2::write_xml(x, vrt_path)
  return(TRUE)
}