def stratify(self, variable):
""" Create a new variable, stratified by the levels of a Factor.
Parameters
----------
variable : str or a simple sympy expression whose string representation
are all lower or upper case letters, i.e. it can be interpreted
as a name
Returns
-------
formula : Formula
Formula whose mean has one parameter named variable%d, for each
level in self.levels
Examples
--------
>>> f = Factor('a', ['x','y'])
>>> sf = f.stratify('theta')
>>> sf.mean
_theta0*a_x + _theta1*a_y
"""
if not set(str(variable)).issubset(lowercase +
uppercase + '0123456789'):
raise ValueError('variable should be interpretable as a '
'name and not have anything but digits '
'and numbers')
variable = sympy.sympify(variable)
f = Formula(self.formula.terms, char=variable)
f.name = self.name
return f
def stratify(factor, variable):
""" Create a new variable, stratified by the levels of a Factor.
Parameters
----------
variable : str or a simple sympy expression whose string representation
are all lower or upper case letters, i.e. it can be interpreted
as a name
Returns
-------
formula : Formula
Formula whose mean has one parameter named _variable%d, for each
level in factor.levels
Examples
--------
>>> f = Factor('a', ['x','y'])
>>> sf = f.stratify('theta')
>>> sf.mean
_theta0*a_x + _theta1*a_y
"""
if not set(str(variable)).issubset(lowercase + uppercase + '0123456789'):
raise ValueError('variable should be interpretable as a '
'name and not have anything but digits '
'and letters')
variable = sympy.sympify(variable)
f = Formula(factor.formula.terms, char=variable)
f.name = factor.name
return f
def formulaVars(self, f: Formula) -> Set[str]:
""" List variables in formula f.
This depends on correct implementation of subf() and Variable.name.
"""
if isinstance(f, Variable):
return set([f.name()])
return set.union(set(), *(self.formulaVars(sf) for sf in f.subf()))
def formulaIsSatisfied(self, f: Formula, v: Valuation):
if isinstance(f, Variable):
return v[f.name()]
elif isinstance(f, Negation):
return not self.formulaIsSatisfied(f.subf()[0], v)
elif isinstance(f, Conjunction):
return all(self.formulaIsSatisfied(sf, v) for sf in f.subf())
elif isinstance(f, Disjunction):
return any(self.formulaIsSatisfied(sf, v) for sf in f.subf())
elif isinstance(f, Implication):
return (not self.formulaIsSatisfied(
f.subf()[0], v)) or self.formulaIsSatisfied(f.subf()[1], v)
elif isinstance(f, Equivalence):
return self.formulaIsSatisfied(f.subf()[0],
v) == self.formulaIsSatisfied(
f.subf()[1], v)
else:
raise TypeError("Formula expected, got %s" % repr(f))
