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author | Cathy Yeh <cathy@driver.xyz> | 2017-12-08 16:00:14 -0800 |
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committer | Cathy Yeh <cathy@driver.xyz> | 2017-12-08 16:00:14 -0800 |
commit | 8cdb00cdb10200e824015ece4a94485e93857352 (patch) | |
tree | ed0aa04912fd227825797b0fa6b89bbab76d5eaa | |
parent | 26b43410569044aff46053cae7c68862825dd4ec (diff) | |
download | beliefs-8cdb00cdb10200e824015ece4a94485e93857352.tar.gz beliefs-8cdb00cdb10200e824015ece4a94485e93857352.tar.bz2 beliefs-8cdb00cdb10200e824015ece4a94485e93857352.zip |
bernoulli AND cpd
-rw-r--r-- | beliefs/factors/bernoulli_and_cpd.py | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/beliefs/factors/bernoulli_and_cpd.py b/beliefs/factors/bernoulli_and_cpd.py new file mode 100644 index 0000000..fb86135 --- /dev/null +++ b/beliefs/factors/bernoulli_and_cpd.py @@ -0,0 +1,42 @@ +import numpy as np + +from beliefs.factors.cpd import TabularCPD + + +class BernoulliAndCPD(TabularCPD): + """CPD class for a Bernoulli random variable whose relationship to its + parents (also Bernoulli random variables) is described by AND logic. + + If all of the variable's parents are True, then the variable + is True, and False otherwise. + """ + def __init__(self, variable, parents=[]): + """ + Args: + variable: int or string + parents: optional, list of int and/or strings + """ + super().__init__(variable=variable, + variable_card=2, + parents=parents, + parents_card=[2]*len(parents), + values=[]) + self._values = [] + + @property + def values(self): + if len(self._values) == 0: + self._values = self._build_kwise_values_array(len(self.variables)) + self._values = self._values.reshape(self.cardinality) + return self._values + + @staticmethod + def _build_kwise_values_array(k): + # special case a completely independent factor, and + # return the uniform prior + if k == 1: + return np.array([0.5, 0.5]) + + return np.array( + [1.]*(2**(k-1)-1) + [0.] + [0.,]*(2**(k-1)-1) + [1.] + ) |