Source code for fca.concept

import numpy as np


class Concept:
    """Implements Formal Concept.

    Formal concept in Context :math:`c` is pair :math:`<A,B>`, where :math:`A`
    is subset of :math:`X`, :math:`B` is subset of :math:`Y` such that
    :math:`c.up(A) = B` and :math:`c.down(B) = A`.

    This formal definition is not required, but you have to include extent
    (objects) and intent (attributes) to create concept.

    Parameters
    ----------
    extent : :py:class:`numpy.array`
        All object (covered by attributes) in concept, empty list is allowed.
        Represented as :py:class:`numpy.array` of bool values.
    intent : :py:class:`numpy.array`
        All attributes (covered by objects) in concept, empty list is allowed.
        Represented as :py:class:`numpy.array` of bool values.

    Attributes
    ----------
    extent : :py:class:`numpy.array`
        All object (covered by attributes) in concept.
        Represented as :py:class:`numpy.array` of bool values.
    intent : :py:class:`numpy.array`
        All attributes (covered by objects) in concept.
        Represented as :py:class:`numpy.array` of bool values.
    """

    def __init__(self, extent, intent):
        self.extent = extent
        self.intent = intent

    def __str__(self):
        return "Concept (Extent: {}, Intent:{})".format(
            str(self.extent), str(self.intent))

    def __repr__(self):
        return "concept({}, {})".format(
            str(self.extent), str(self.intent))

    def __eq__(self, other):
        if isinstance(self, other.__class__):
            return (np.array_equal(self.extent, other.extent) and
                    np.array_equal(self.intent, other.intent))

        return False

    def __hash__(self):
        return hash(str((self.extent, self.intent)))

    def human_readable(self, context):
        """Return human readable strings of extent and intent"""

        intent = context.data_frame.columns.base[self.intent]
        extent = context.data_frame.index.base[self.extent]

        return extent, intent

    @staticmethod
    def save_list(list_of_concepts, outfile):
        """save list of concepts into file via numpy.savez"""

        return np.savez(outfile, np.array(list_of_concepts))

    @staticmethod
    def load_list(infile):
        """load list of concepts from file via numpy.load"""

        loaded = np.load(infile)

        for arr in loaded.files:
            return list(loaded[arr])