uncertainties

September 20, 2024 ยท View on GitHub

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The uncertainties package allows calculations with values that have uncertaintes, such as (2 +/- 0.1)*2 = 4 +/- 0.2. uncertainties takes the pain and complexity out of error propagation and calculations of values with uncertainties. For more information, see https://uncertainties.readthedocs.io/

Basic examples

.. code-block:: python

>>> from uncertainties import ufloat
>>> x = ufloat(2, 0.25)
>>> x
2.0+/-0.25

>>> square = x**2
>>> square
4.0+/-1.0
>>> square.nominal_value
4.0
>>> square.std_dev  # Standard deviation
1.0

>>> square - x*x
0.0  # Exactly 0: correlations taken into account

>>> from uncertainties.umath import sin, cos  # and many more.
>>> sin(1+x**2)
-0.95892427466313845+/-0.2836621854632263

>>> print (2*x+1000).derivatives[x]  # Automatic calculation of derivatives
2.0

>>> from uncertainties import unumpy  # Array manipulation
>>> varr = unumpy.uarray([1, 2], [0.1, 0.2])
>>> print(varr)
[1.0+/-0.1 2.0+/-0.2]
>>> print(varr.mean())
1.50+/-0.11
>>> print(unumpy.cos(varr))
[0.540302305868+/-0.0841470984808 -0.416146836547+/-0.181859485365]

Main features

  • Transparent calculations with uncertainties: Little or no modification of existing code is needed to convert calculations of floats to calculations of values with uncertainties.

  • Correlations between expressions are correctly taken into account. Thus, x-x is exactly zero.

  • Most mathematical operations are supported, including most functions from the standard math_ module (sin,...). Comparison operators (>, ==, etc.) are supported too.

  • Many fast operations on arrays and matrices of numbers with uncertainties are supported.

  • Extensive support for printing numbers with uncertainties (including LaTeX support and pretty-printing).

  • Most uncertainty calculations are performed analytically.

  • This module also gives access to the derivatives of any mathematical expression (they are used by error propagation theory_, and are thus automatically calculated by this module).

Installation or upgrade

To install uncertainties, use::

 pip install uncertainties

To upgrade from an older version, use::

 pip install --upgrade uncertainties

Further details are in the on-line documentation <https://uncertainties.readthedocs.io/en/latest/install.html>_.

Git branches

The GitHub master branch is the latest development version, and is intended to be a stable pre-release version. It will be experimental, but should pass all tests.. Tagged releases will be available on GitHub, and correspond to the releases to PyPI. The GitHub gh-pages branch will contain a stable test version of the documentation that can be viewed at <https://lmfit.github.io/uncertainties/>_. Other Github branches should be treated as unstable and in-progress development branches.

License

This package and its documentation are released under the Revised BSD License <LICENSE.txt>_.

History

.. Note from Eric Lebigot: I would like the origin of the package to remain documented for its whole life. Thanks!

This package was created back around 2009 by Eric O. LEBIGOT <https://github.com/lebigot>_.

Ownership of the package was taken over by the lmfit GitHub organization <https://github.com/lmfit>_ in 2024.

.. _IPython: https://ipython.readthedocs.io/en/stable/ .. _math: https://docs.python.org/library/math.html .. _error propagation theory: https://en.wikipedia.org/wiki/Propagation_of_uncertainty .. _main website: https://uncertainties.readthedocs.io/