def parent_values(
self, cbn: CausalBayesianNetwork) -> Iterator[Dict[str, Outcome]]:
"""Return a list of lists for the values each parent can take (based on the parent state names)"""
parent_values_list = []
for p in cbn.get_parents(self.variable):
try:
parent_values_list.append(cbn.model.domain[p])
except KeyError:
raise ParentsNotReadyException(
f"Parent {p} of {self.variable} not yet instantiated")
for parent_values in itertools.product(*parent_values_list):
yield {
p.lower(): parent_values[i]
for i, p in enumerate(cbn.get_parents(self.variable))
}
def initialize_tabular_cpd(self, cbn: CausalBayesianNetwork) -> None:
"""Initialize the probability table for the inherited TabularCPD.
Requires that all parents in the CID have already been instantiated.
"""
self.check_function_arguments_match_parent_names(cbn)
self.cbn = cbn
if self.force_domain:
if not set(self.possible_values(cbn)).issubset(self.force_domain):
raise ValueError(
"variable {} can take value outside given state_names".
format(self.variable))
domain: Sequence[
Outcome] = self.force_domain if self.force_domain else self.possible_values(
cbn)
def complete_prob_dictionary(
prob_dictionary: Dict[Outcome, Union[int, float]]
) -> Dict[Outcome, Union[int, float]]:
"""Complete a probability dictionary with probabilities for missing outcomes"""
missing_outcomes = set(domain) - set(prob_dictionary.keys())
missing_prob_mass = 1 - sum(
prob_dictionary.values()) # type: ignore
for outcome in missing_outcomes:
prob_dictionary[outcome] = missing_prob_mass / len(
missing_outcomes)
return prob_dictionary
card = len(domain)
evidence = cbn.get_parents(self.variable)
evidence_card = [cbn.get_cardinality(p) for p in evidence]
probability_list = []
for pv in self.parent_values(cbn):
probabilities = complete_prob_dictionary(
self.stochastic_function(**pv))
probability_list.append([probabilities[t] for t in domain])
probability_matrix = np.array(probability_list).T
if not np.allclose(probability_matrix.sum(axis=0), 1, atol=0.01):
raise ValueError(
f"The values for {self.variable} do not sum to 1 \n{probability_matrix}"
)
if (probability_matrix < 0).any() or (probability_matrix > 1).any():
raise ValueError(
f"The probabilities for {self.variable} are not within range 0-1\n{probability_matrix}"
)
self.domain = domain
super().__init__(self.variable,
card,
probability_matrix,
evidence,
evidence_card,
state_names={self.variable: self.domain})
def check_function_arguments_match_parent_names(
self, cbn: CausalBayesianNetwork) -> None:
"""Raises a ValueError if the parents in the CID don't match the argument to the specified function"""
sig = inspect.signature(self.stochastic_function).parameters
arg_kinds = [arg_kind.kind.name for arg_kind in sig.values()]
args = set(sig)
lower_case_parents = {
p.lower()
for p in cbn.get_parents(self.variable)
}
if "VAR_KEYWORD" not in arg_kinds and args != lower_case_parents:
raise ValueError(
f"function for {self.variable} mismatch parents on"
f" {args.symmetric_difference(lower_case_parents)}, ")
def __init__(
self,
variable: str,
stochastic_function: Callable[..., Union[Outcome, Mapping[Outcome, Union[int, float]]]],
cbn: CausalBayesianNetwork,
domain: Optional[Sequence[Outcome]] = None,
label: str = None,
) -> None:
"""Initialize StochasticFunctionCPD with a variable name and a stochastic function.
Parameters
----------
variable: The variable name.
stochastic_function: A stochastic function that maps parent outcomes to a distribution
over outcomes for this variable (see doc-string for class).
The different parents are identified by name: the arguments to the function must
be lowercase versions of the names of the parent variables. For example, if X has
parents Y, S1, and Obs, the arguments to function must be y, s1, and obs.
domain: An optional specification of the variable's domain.
Must include all values this variable can take as a result of its function.
label: An optional label used to describe this distribution.
"""
self.variable = variable
self.func = stochastic_function
self.cbn = cbn
assert isinstance(domain, (list, type(None)))
self.force_domain: Optional[Sequence[Outcome]] = domain
assert isinstance(label, (str, type(None)))
self.label = label if label is not None else self.compute_label(stochastic_function)
self.check_function_arguments_match_parent_names()
if self.force_domain:
if not set(self.possible_values()).issubset(self.force_domain):
raise ValueError("variable {} can take value outside given state_names".format(self.variable))
self.domain = self.force_domain if self.force_domain else self.possible_values()
def complete_prob_dictionary(
prob_dictionary: Mapping[Outcome, Union[int, float]]
) -> Mapping[Outcome, Union[int, float]]:
"""Complete a probability dictionary with probabilities for missing outcomes"""
prob_dictionary = {key: value for key, value in prob_dictionary.items() if value is not None}
missing_outcomes = set(self.domain) - set(prob_dictionary.keys())
missing_prob_mass = 1 - sum(prob_dictionary.values()) # type: ignore
for outcome in missing_outcomes:
prob_dictionary[outcome] = missing_prob_mass / len(missing_outcomes)
return prob_dictionary
card = len(self.domain)
evidence = cbn.get_parents(self.variable)
evidence_card = [cbn.get_cardinality(p) for p in evidence]
probability_list = []
for pv in self.parent_values():
probabilities = complete_prob_dictionary(self.stochastic_function(**pv))
probability_list.append([probabilities[t] for t in self.domain])
probability_matrix = np.array(probability_list).T
if not np.allclose(probability_matrix.sum(axis=0), 1, rtol=0, atol=0.01): # type: ignore
raise ValueError(f"The values for {self.variable} do not sum to 1 \n{probability_matrix}")
if (probability_matrix < 0).any() or (probability_matrix > 1).any(): # type: ignore
raise ValueError(f"The probabilities for {self.variable} are not within range 0-1\n{probability_matrix}")
super().__init__(
self.variable, card, probability_matrix, evidence, evidence_card, state_names={self.variable: self.domain}
)