Source code for bw2calc.indexing

# -*- coding: utf-8 -*-
from __future__ import print_function, unicode_literals
from eight import *

from .utils import MAX_INT_32
import itertools
import numpy as np




[docs]
def index_with_arrays(array_from, array_to, mapping):
    """Map ``array_from`` keys to ``array_to`` values using the dictionary ``mapping``.

    Turns the keys and values of mapping into index arrays.

    This is needed to take the ``flow``, ``input``, and ``output`` columns, which can be arbitrarily large integers, and transform them to matrix indices, which start from zero.

    Here is an example:

    .. code-block:: python

        import numpy as np
        a_f = np.array((1, 2, 3, 4))
        a_t = np.zeros(4)
        mapping = {1: 5, 2: 6, 3: 7, 4: 8}
        index_with_arrays(a_f, a_t, mapping)
        # => a_t is now [5, 6, 7, 8]

    Args:
        * *array_from* (array): 1-dimensional integer numpy array.
        * *array_to* (array): 1-dimensional integer numpy array.
        * *mapping* (dict): Dictionary that links ``mapping`` indices to ``row`` or ``col`` indices, e.g. ``{34: 3}``.

    Operates in place. Doesn't return anything."""
    keys = np.array(list(mapping.keys()))
    values = np.array(list(mapping.values()))

    if keys.min() < 0:
        raise ValueError("Keys must be positive integers")

    index_array = np.zeros(keys.max() + 1) + MAX_INT_32
    index_array[keys] = values

    mask = array_from <= keys.max()
    array_to[:] = MAX_INT_32
    array_to[mask] = index_array[array_from[mask]]






[docs]
def index_with_searchsorted(array_from, array_to):
    """Build a dictionary from the sorted, unique elements of an array, and map this dictionary from ``array_from`` to ``array_to``.

    Adapted from http://stackoverflow.com/questions/3403973/fast-replacement-of-values-in-a-numpy-array.

    Here is an example:

    .. code-block:: python

        import numpy as np
        array = np.array((4, 8, 6, 2, 4))
        output = np.zeros(5)
        index_with_searchsorted(array, output)
        # => returns {2: 0, 4: 1, 6: 2, 8: 3}
        # and `output` is [1, 3, 2, 0, 1]

    ``array_from`` and ``array_to`` are arrays of integers.

    Returns a dictionary that maps the sorted, unique elements of ``array_from`` to integers starting with zero."""
    unique = np.unique(array_from)
    idx = np.searchsorted(unique, array_from)
    array_to[:] = idx
    return dict(zip(
        (int(x) for x in unique),
        itertools.count()
    ))
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