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Compare the structure of two netCDF files at the command line

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ncompare


Compare the structure of two NetCDF files at the command line. ncompare generates a view of the matching and non-matching groups and variables between two NetCDF datasets.

Motivation

The cdo (climate data operators) tool does not support NetCDF4 groups. Moreover, nco operators' ncdiff function computes value differences, but --- as far as the developers of this tool are aware --- nco does not have a simple function to show structural differences between NetCDF4 datasets.

Initial setup -- installing with dependencies

Option A) Install using poetry:

i) Follow the instructions for installing poetry here.

ii) Run poetry install from the repository directory.

Option B) Install using pip:

i) Run pip install . from the repository directory.

Basic usage at a command line:

If installed using a poetry environment:

poetry run ncompare <netcdf file #1> <netcdf file #2>

Otherwise:

ncompare <netcdf file #1> <netcdf file #2>

Example: ncompare S001G01.nc S001G01_SUBSET.nc -g product -v ozone_profile --report subset_comparison.txt

Options

  • --file-text [FILE_PATH]: Text file to write output to.
  • --file-csv [FILE_PATH]: Comma separated values (CSV) file to write output to.
  • --file-xlsx [FILE_PATH]: Excel file to write output to.
  • --no-color : Turn off all colorized output.
  • --show-attributes : Include variable attributes in the table that compares variables.
  • --show-chunks : Include chunk sizes in the table that compares variables.
  • -v (--comparison_var_name) [VAR_NAME]: Compare specific values for this variable.
  • -g (--comparison_var_group) [VAR_GROUP]: Group that contains the comparison_var_name.

How to test ncompare locally

If installed using a poetry environment, the tests can be run with:

poetry run pytest tests

Known limitations

  • This currently works with netCDF hierarchies containing no more than one level of groups.
  • This uses xarray to access the root-level dimensions. In some cases, xarray will miss dimensions whose names do not also exist as variable names in the dataset (also known as non-coordinate dimensions).

Notices:

Copyright 2023 United States Government as represented by the Administrator of the National Aeronautics and Space Administration. All Rights Reserved.

Third-Party Software:

This software calls the following third-party software, which is subject to the terms and conditions of its licensor, as applicable at the time of licensing. Third-party software is not bundled with this software, but may be available from the licensor.

License hyperlinks are provided here for information purposes only:

item license link
colorama BSD-3-Clause https://opensource.org/licenses/BSD-3-Clause
netCDF4 MIT License https://opensource.org/licenses/MIT
numpy BSD-3-Clause https://opensource.org/licenses/BSD-3-Clause
openpyxl MIT License https://opensource.org/licenses/MIT
xarray Apache License, version 2.0 https://www.apache.org/licenses/LICENSE-2.0
Python Standard Library Python Software Foundation (PSF) License Agreement https://docs.python.org/3/license.html#psf-licenseDisclaimers

No Warranty:

THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE. THIS AGREEMENT DOES NOT, IN ANY MANNER, CONSTITUTE AN ENDORSEMENT BY GOVERNMENT AGENCY OR ANY PRIOR RECIPIENT OF ANY RESULTS, RESULTING DESIGNS, HARDWARE, SOFTWARE PRODUCTS OR ANY OTHER APPLICATIONS RESULTING FROM USE OF THE SUBJECT SOFTWARE.
FURTHER, GOVERNMENT AGENCY DISCLAIMS ALL WARRANTIES AND LIABILITIES REGARDING THIRD-PARTY SOFTWARE, IF PRESENT IN THE ORIGINAL SOFTWARE, AND DISTRIBUTES IT "AS IS."

Waiver and Indemnity:

RECIPIENT AGREES TO WAIVE ANY AND ALL CLAIMS AGAINST THE UNITED STATES GOVERNMENT, ITS CONTRACTORS AND SUBCONTRACTORS, AS WELL AS ANY PRIOR RECIPIENT. IF RECIPIENT'S USE OF THE SUBJECT SOFTWARE RESULTS IN ANY LIABILITIES, DEMANDS, DAMAGES, EXPENSES OR LOSSES ARISING FROM SUCH USE, INCLUDING ANY DAMAGES FROM PRODUCTS BASED ON, OR RESULTING FROM, RECIPIENT'S USE OF THE SUBJECT SOFTWARE, RECIPIENT SHALL INDEMNIFY AND HOLD HARMLESS THE UNITED STATES GOVERNMENT, ITS CONTRACTORS AND SUBCONTRACTORS, AS WELL AS ANY PRIOR RECIPIENT, TO THE EXTENT PERMITTED BY LAW. RECIPIENT'S SOLE REMEDY FOR ANY SUCH MATTER SHALL BE THE IMMEDIATE, UNILATERAL TERMINATION OF THIS AGREEMENT.

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