Source code for fraud_eagle.prior

#
# prior.py
#
# Copyright (c) 2016-2017 Junpei Kawamoto
#
# This file is part of rgmining-fraud-eagle.
#
# rgmining-fraud-eagle is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# rgmining-fraud-eagle is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with rgmining-fraud-eagle. If not, see <http://www.gnu.org/licenses/>.
#
"""Define prior beliefs of users and products.
"""
from __future__ import absolute_import
import numpy as np
from fraud_eagle.constants import HONEST, FRAUD, GOOD, BAD

_LOG_2 = np.log(2.)
"""Precomputed value, the logarithm of 2.0."""


[docs]def phi_u(user): """Logarithm of a prior belief of a user. The definition is .. math:: \\phi_{i}^{\\cal{U}}: \\cal{L}_{\\cal{U}} \\rightarrow \\mathbb{R}_{\\geq 0}, where :math:`\\cal{U}` is a set of user nodes, :math:`\\cal{L}_{\\cal{U}}` is a set of user labels, and :math:`\\mathbb{R}_{\\geq 0}` is a set of real numbers grater or equals to :math:`0`. The implementation of this mapping is given as .. math:: \\phi_{i}^{\\cal{U}}(y_{i}) \\leftarrow \\|\\cal{L}_{\\cal{U}}\\|. On the other hand, :math:`\\cal{L}_{\\cal{U}}` is given as {honest, fraud}. It means the mapping returns :math:`\\phi_{i} = 2` for any user. This function returns the logarithm of such :math:`\\phi_{i}`, i.e. :math:`\\log(\\phi_{i}(u))` for any user :math:`u`. Args: user: User object. Returns: The logarithm of the prior belief of the label of the given user. However, it returns :math:`\\log 2` whatever the given user is. """ if user in (HONEST, FRAUD): return _LOG_2 raise ValueError("Invalid user label:", user)
[docs]def phi_p(product): """Logarithm of a prior belief of a product. The definition is .. math:: \\phi_{j}^{\\cal{P}}: \\cal{L}_{\\cal{P}} \\rightarrow \\mathbb{R}_{\\geq 0}, where :math:`\\cal{P}` is a set of produce nodes, :math:`\\cal{L}_{\\cal{P}}` is a set of product labels, and :math:`\\mathbb{R}_{\\geq 0}` is a set of real numbers grater or equals to :math:`0`. The implementation of this mapping is given as .. math:: \\phi_{j}^{\\cal{P}}(y_{j}) \\leftarrow \\|\\cal{L}_{\\cal{P}}\\|. On the other hand, :math:`\\cal{L}_{\\cal{P}}` is given as {good, bad}. It means the mapping returns :math:`2` despite the given product. This function returns the logarithm of such :math:`\\phi_{j}`, i.e. :math:`\\log(\\phi_{j}(p))` for any product :math:`p`. Args: user: Product object. Returns: The logarithm of the prior belief of the label of the given product. However, it returns :math:`\\log 2` whatever the given product is. """ if product in (GOOD, BAD): return _LOG_2 raise ValueError("Invalid product label:", product)