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:

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