Source code for libpgm.CPDtypes.crazy

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'''
This module contains tools for representing "crazy" nodes -- nodes where the method for sampling is to multiply the crazyinput by -10 or 10 and add :math:`\pi` -- as class instances with their own *choose* method to choose an outcome for themselves based on parent outcomes. 

The existence of this 'crazy' type is meant to indicate the true universality of
the universal sampling method found in :doc:`hybayesiannetwork`. While no CPD would
actually be this crazy, the libary has the setup to support any type of CPD.


'''
import math
import random

class Crazy():
    '''
    This class represents a crazy node, as described above. It contains the *Vdataentry* attribute and the *choose* method.

    '''
    def __init__(self, Vdataentry):
        '''
        This class is constructed with the argument *Vdataentry* which must be a dict containing a dictionary entry for this particualr node. The dict must contain an entry of the following form::

            "crazyinput": <number that is the crazy input>

        This ``"crazyinput"`` entry contains the number that will be used in the crazy sampling function.  The *Vdataentry* attribute is set equal to this *Vdataentry* input upon instantiation.
        '''
        self.Vdataentry = Vdataentry
        '''A dict containing CPD data for the node.'''
        
    def choose(self, pvalues):
        '''
        Randomly choose state of node from probability distribution conditioned on *pvalues*.

        This method has two parts: (1) determining the proper probability
        distribution, and (2) using that probability distribution to determine
        an outcome.

        Arguments:
            1. *pvalues* -- An array containing the assigned states of the node's parents. This must be in the same order as the parents appear in self.Vdataentry['parents'].

        The function takes the crazyinput, multiplies it by either 10 or -10 randomly, adds :math:`\\pi`, converts it to a string, and appends the word "bluberries!". It returns this value.

        '''
        crazyinput = self.Vdataentry["crazyinput"]
        answer = "%.2f blueberries!" % (random.choice([10, -10]) * crazyinput + math.pi)
        return answer