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# Copyright (c) 2008-2016 MetPy Developers. |
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# Distributed under the terms of the BSD 3-Clause License. |
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# SPDX-License-Identifier: BSD-3-Clause |
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r"""Module to provide unit support. |
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This makes use of the :mod:`pint` library and sets up the default settings |
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for good temperature support. |
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Attributes |
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---------- |
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units : :class:`pint.UnitRegistry` |
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The unit registry used throughout the package. Any use of units in MetPy should |
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import this registry and use it to grab units. |
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""" |
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from __future__ import division |
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import numpy as np |
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import pint |
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import pint.unit |
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UndefinedUnitError = pint.UndefinedUnitError |
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units = pint.UnitRegistry(autoconvert_offset_to_baseunit=True) |
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# For pint 0.6, this is the best way to define a dimensionless unit. See pint #185 |
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units.define(pint.unit.UnitDefinition('percent', '%', (), |
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pint.converters.ScaleConverter(0.01))) |
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def concatenate(arrs, axis=0): |
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r"""Concatenate multiple values into a new unitized object. |
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This is essentially a unit-aware version of `numpy.concatenate`. All items |
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must be able to be converted to the same units. If an item has no units, it will be given |
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those of the rest of the collection, without conversion. The first units found in the |
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arguments is used as the final output units. |
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Parameters |
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---------- |
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arrs : Sequence of arrays |
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The items to be joined together |
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axis : integer, optional |
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The array axis along which to join the arrays. Defaults to 0 (the first dimension) |
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Returns |
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------- |
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`pint.Quantity` |
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New container with the value passed in and units corresponding to the first item. |
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""" |
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dest = 'dimensionless' |
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for a in arrs: |
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if hasattr(a, 'units'): |
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dest = a.units |
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break |
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data = [] |
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for a in arrs: |
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if hasattr(a, 'to'): |
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a = a.to(dest).magnitude |
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data.append(np.atleast_1d(a)) |
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return units.Quantity(np.concatenate(data, axis=axis), dest) |
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def atleast_1d(*arrs): |
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r"""Convert inputs to arrays with at least one dimension. |
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Scalars are converted to 1-dimensional arrays, whilst other |
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higher-dimensional inputs are preserved. This is a thin wrapper |
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around `numpy.atleast_1d` to preserve units. |
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Parameters |
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---------- |
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arrs : arbitrary positional arguments |
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Input arrays to be converted if necessary |
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Returns |
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------- |
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`pint.Quantity` |
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A single quantity or a list of quantities, matching the number of inputs. |
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""" |
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mags = [a.magnitude for a in arrs] |
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orig_units = [a.units for a in arrs] |
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ret = np.atleast_1d(*mags) |
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if len(mags) == 1: |
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return units.Quantity(ret, orig_units[0]) |
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return [units.Quantity(m, u) for m, u in zip(ret, orig_units)] |
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def atleast_2d(*arrs): |
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r"""Convert inputs to arrays with at least two dimensions. |
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Scalars and 1-dimensional arrays are converted to 2-dimensional arrays, |
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whilst other higher-dimensional inputs are preserved. This is a thin wrapper |
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around `numpy.atleast_2d` to preserve units. |
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Parameters |
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---------- |
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arrs : arbitrary positional arguments |
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Input arrays to be converted if necessary |
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Returns |
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------- |
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`pint.Quantity` |
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A single quantity or a list of quantities, matching the number of inputs. |
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""" |
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mags = [a.magnitude for a in arrs] |
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orig_units = [a.units for a in arrs] |
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ret = np.atleast_2d(*mags) |
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if len(mags) == 1: |
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return units.Quantity(ret, orig_units[0]) |
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return [units.Quantity(m, u) for m, u in zip(ret, orig_units)] |
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def masked_array(data, data_units=None, **kwargs): |
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"""Create a :class:`numpy.ma.MaskedArray` with units attached. |
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This is a thin wrapper around :func:`numpy.ma.masked_array` that ensures that |
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units are properly attached to the result (otherwise units are silently lost). Units |
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are taken from the ``units`` argument, or if this is ``None``, the units on ``data`` |
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are used. |
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Parameters |
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---------- |
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data : array_like |
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The source data. If ``units`` is `None`, this should be a `pint.Quantity` with |
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the desired units. |
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data_units : str or `pint.Unit` |
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The units for the resulting `pint.Quantity` |
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**kwargs : Arbitrary keyword arguments passed to `numpy.ma.masked_array` |
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Returns |
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------- |
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`pint.Quantity` |
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""" |
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if data_units is None: |
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data_units = data.units |
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return units.Quantity(np.ma.masked_array(data, **kwargs), data_units) |
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del pint |
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Unidata /
MetPy
