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Extract and Select Subdataset Information from a Raster File

gdal_info_table.Rd

This function runs gdalUtilities::gdalinfo(file, json = TRUE) to get structured information about a raster file, specifically extracting details about any subdatasets (common in formats like NetCDF or HDF). It parses the subdataset name and description fields to create a summary table.

Usage

gdal_info_table(file, interactive = FALSE, ...)

Arguments

file

Character string. Path to the raster file (e.g., NetCDF, HDF).

interactive

Logical. If TRUE and the session is interactive, prompts the user to select subdatasets via a graphical list (if available) or text menu. Default: FALSE.

...

Additional arguments passed verbatim to gdalUtilities::gdalinfo(). Note that json = TRUE is automatically added.

Value

A list with two elements:

table

A data frame containing information for each subdataset found, with columns typically including index, name (full GDAL name), variable (derived variable name), description, dimensions, and data_type. Returns an empty data frame with these columns if no subdatasets are found.

selected

A character vector containing the variable names of the subdatasets selected by the user. Empty if interactive = FALSE or no selection is made.

Details

Uses gdalUtilities::gdalinfo with JSON output to extract subdataset #' information into a tidy data frame. Optionally allows interactive selection. #'

Examples

if (FALSE) { # \dontrun{
# Create a dummy NetCDF file for demonstration if needed
# (Requires the ncdf4 package)
if (requireNamespace("ncdf4", quietly = TRUE)) {
  tmp_nc_file = tempfile(fileext = ".nc")
  dimX = ncdf4::ncdim_def("x", "meters", 1:10)
  dimY = ncdf4::ncdim_def("y", "meters", 1:5)
  var1 = ncdf4::ncvar_def("temp", "degrees_C", list(dimX, dimY), -999,
                          "Temperature variable")
  var2 = ncdf4::ncvar_def("precip", "mm", list(dimX, dimY), -999,
                          "Precipitation variable")
  nc_out = ncdf4::nc_create(tmp_nc_file, list(var1, var2))
  ncdf4::nc_close(nc_out)

  # --- Example Usage ---

  # 1. Extract subdataset table (non-interactive)
  info_list = gdal_info_table(tmp_nc_file)
  print(info_list$table)

  # 2. Extract and potentially select interactively
  # (Will only prompt if run in an interactive R session)
  selected_info = gdal_info_table(tmp_nc_file, interactive = TRUE)
  if (length(selected_info$selected) > 0) {
    cat("\nSelected variables:\n")
    print(selected_info$selected)
  } else if (interactive()) {
    cat("\nNo variables selected interactively.\n")
  }

  # Clean up dummy file
  unlink(tmp_nc_file)
} else {
  message("Skipping examples: ncdf4 package not available to create test file.")
}

# Example with a potentially non-existent file (will error)
try(gdal_info_table("non_existent_file.nc"))
} # }