def construct_mediation_estimand(self, estimand_type, treatment_name,
outcome_name, mediators_names):
# TODO: support multivariate treatments better.
expr = None
if estimand_type in (CausalIdentifier.NONPARAMETRIC_NDE,
CausalIdentifier.NONPARAMETRIC_NIE):
outcome_name = outcome_name[0]
sym_outcome = spstats.Normal(outcome_name, 0, 1)
sym_treatment_symbols = [
spstats.Normal(t, 0, 1) for t in treatment_name
]
sym_treatment = sp.Array(sym_treatment_symbols)
sym_mediators_symbols = [
sp.Symbol(inst) for inst in mediators_names
]
sym_mediators = sp.Array(sym_mediators_symbols)
sym_outcome_derivative = sp.Derivative(sym_outcome, sym_mediators)
sym_treatment_derivative = sp.Derivative(sym_mediators,
sym_treatment)
# For direct effect
num_expr_str = outcome_name
if len(mediators_names) > 0:
num_expr_str += "|" + ",".join(mediators_names)
sym_mu = sp.Symbol("mu")
sym_sigma = sp.Symbol("sigma", positive=True)
sym_conditional_outcome = spstats.Normal(num_expr_str, sym_mu,
sym_sigma)
sym_directeffect_derivative = sp.Derivative(
sym_conditional_outcome, sym_treatment)
if estimand_type == CausalIdentifier.NONPARAMETRIC_NIE:
sym_effect = spstats.Expectation(sym_treatment_derivative *
sym_outcome_derivative)
elif estimand_type == CausalIdentifier.NONPARAMETRIC_NDE:
sym_effect = spstats.Expectation(sym_directeffect_derivative)
sym_assumptions = {
"Mediation":
("{2} intercepts (blocks) all directed paths from {0} to {1} except the path {{{0}}}\N{RIGHTWARDS ARROW}{{{1}}}."
).format(",".join(treatment_name), ",".join(outcome_name),
",".join(mediators_names)),
"First-stage-unconfoundedness":
(u"If U\N{RIGHTWARDS ARROW}{{{0}}} and U\N{RIGHTWARDS ARROW}{{{1}}}"
" then P({1}|{0},U) = P({1}|{0})").format(
",".join(treatment_name), ",".join(mediators_names)),
"Second-stage-unconfoundedness":
(u"If U\N{RIGHTWARDS ARROW}{{{2}}} and U\N{RIGHTWARDS ARROW}{1}"
" then P({1}|{2}, {0}, U) = P({1}|{2}, {0})").format(
",".join(treatment_name), outcome_name,
",".join(mediators_names))
}
else:
raise ValueError(
"Estimand type not supported. Supported estimand types are {0} or {1}'."
.format(CausalIdentifier.NONPARAMETRIC_NDE,
CausalIdentifier.NONPARAMETRIC_NIE))
estimand = {'estimand': sym_effect, 'assumptions': sym_assumptions}
return estimand
def construct_symbolic_estimator(self, estimand):
sym_outcome = (spstats.Normal(",".join(estimand.outcome_variable), 0,
1))
sym_treatment = (spstats.Normal(",".join(estimand.treatment_variable),
0, 1))
sym_instrument = sp.Symbol(estimand.instrumental_variables[0])
sym_outcome_derivative = sp.Derivative(sym_outcome, sym_instrument)
sym_treatment_derivative = sp.Derivative(sym_treatment, sym_instrument)
sym_effect = (spstats.Expectation(sym_outcome_derivative) /
sp.stats.Expectation(sym_treatment_derivative))
estimator_assumptions = {
"treatment_effect_homogeneity":
("Each unit's treatment {0} is".format(self._treatment_name) +
"affected in the same way by common causes of "
"{0} and {1}".format(self._treatment_name, self._outcome_name)),
"outcome_effect_homogeneity":
("Each unit's outcome {0} is".format(self._outcome_name) +
"affected in the same way by common causes of "
"{0} and {1}".format(self._treatment_name, self._outcome_name)),
}
sym_assumptions = {
**estimand.estimands["iv"]["assumptions"],
**estimator_assumptions
}
symbolic_estimand = RealizedEstimand(estimand,
estimator_name="Wald Estimator")
symbolic_estimand.update_assumptions(sym_assumptions)
symbolic_estimand.update_estimand_expression(sym_effect)
return symbolic_estimand
def construct_backdoor_estimand(self, estimand_type, treatment_name,
outcome_name, common_causes):
# TODO: outputs string for now, but ideally should do symbolic
# expressions Mon 19 Feb 2018 04:54:17 PM DST
expr = None
if estimand_type == "ate":
num_expr_str = outcome_name + "|"
num_expr_str += ",".join(common_causes)
expr = "d(" + num_expr_str + ")/d" + treatment_name
sym_mu = sp.Symbol("mu")
sym_sigma = sp.Symbol("sigma", positive=True)
sym_outcome = spstats.Normal(num_expr_str, sym_mu, sym_sigma)
# sym_common_causes = [sp.stats.Normal(common_cause, sym_mu, sym_sigma) for common_cause in common_causes]
sym_treatment = sp.Symbol(treatment_name)
sym_conditional_outcome = spstats.Expectation(sym_outcome)
sym_effect = sp.Derivative(sym_conditional_outcome, sym_treatment)
sym_assumptions = {
'Unconfoundedness': (
u"If U\N{RIGHTWARDS ARROW}{0} and U\N{RIGHTWARDS ARROW}{1}"
" then P({1}|{0},{2},U) = P({1}|{0},{2})"
).format(treatment_name, outcome_name, ",".join(common_causes))
}
estimand = {
'estimand': sym_effect,
'assumptions': sym_assumptions
}
return estimand
def construct_iv_estimand(self, estimand_type, treatment_name,
outcome_name, instrument_names):
expr = None
if estimand_type == "ate":
sym_outcome = spstats.Normal(outcome_name, 0, 1)
sym_treatment = spstats.Normal(treatment_name, 0, 1)
sym_instrument = sp.Symbol(instrument_names[0]) # ",".join(instrument_names))
sym_outcome_derivative = sp.Derivative(sym_outcome, sym_instrument)
sym_treatment_derivative = sp.Derivative(sym_treatment, sym_instrument)
sym_effect = spstats.Expectation(sym_outcome_derivative / sym_treatment_derivative)
sym_assumptions = {
"As-if-random": (
"If U\N{RIGHTWARDS ARROW}\N{RIGHTWARDS ARROW}{0} then "
"\N{NOT SIGN}(U \N{RIGHTWARDS ARROW}\N{RIGHTWARDS ARROW}{1})"
).format(outcome_name, ",".join(instrument_names)),
"Exclusion": (
u"If we remove {{{0}}}\N{RIGHTWARDS ARROW}{1}, then "
u"\N{NOT SIGN}({0}\N{RIGHTWARDS ARROW}{2})"
).format(",".join(instrument_names), treatment_name,
outcome_name)
}
estimand = {
'estimand': sym_effect,
'assumptions': sym_assumptions
}
return estimand
def construct_iv_estimand(self, estimand_type, treatment_name,
outcome_name, instrument_names):
# TODO: support multivariate treatments better.
expr = None
outcome_name = outcome_name[0]
sym_outcome = spstats.Normal(outcome_name, 0, 1)
sym_treatment_symbols = [
spstats.Normal(t, 0, 1) for t in treatment_name
]
sym_treatment = sp.Array(sym_treatment_symbols)
sym_instrument_symbols = [sp.Symbol(inst) for inst in instrument_names]
sym_instrument = sp.Array(
sym_instrument_symbols) # ",".join(instrument_names))
sym_outcome_derivative = sp.Derivative(sym_outcome, sym_instrument)
sym_treatment_derivative = sp.Derivative(sym_treatment, sym_instrument)
sym_effect = spstats.Expectation(sym_outcome_derivative /
sym_treatment_derivative)
sym_assumptions = {
"As-if-random":
("If U\N{RIGHTWARDS ARROW}\N{RIGHTWARDS ARROW}{0} then "
"\N{NOT SIGN}(U \N{RIGHTWARDS ARROW}\N{RIGHTWARDS ARROW}{{{1}}})"
).format(outcome_name, ",".join(instrument_names)),
"Exclusion":
(u"If we remove {{{0}}}\N{RIGHTWARDS ARROW}{{{1}}}, then "
u"\N{NOT SIGN}({{{0}}}\N{RIGHTWARDS ARROW}{2})").format(
",".join(instrument_names), ",".join(treatment_name),
outcome_name)
}
estimand = {'estimand': sym_effect, 'assumptions': sym_assumptions}
return estimand
def construct_backdoor_estimand(self, estimand_type, treatment_name,
outcome_name, common_causes):
# TODO: outputs string for now, but ideally should do symbolic
# expressions Mon 19 Feb 2018 04:54:17 PM DST
# TODO Better support for multivariate treatments
expr = None
outcome_name = outcome_name[0]
num_expr_str = outcome_name
if len(common_causes) > 0:
num_expr_str += "|" + ",".join(common_causes)
expr = "d(" + num_expr_str + ")/d" + ",".join(treatment_name)
sym_mu = sp.Symbol("mu")
sym_sigma = sp.Symbol("sigma", positive=True)
sym_outcome = spstats.Normal(num_expr_str, sym_mu, sym_sigma)
sym_treatment_symbols = [sp.Symbol(t) for t in treatment_name]
sym_treatment = sp.Array(sym_treatment_symbols)
sym_conditional_outcome = spstats.Expectation(sym_outcome)
sym_effect = sp.Derivative(sym_conditional_outcome, sym_treatment)
sym_assumptions = {
'Unconfoundedness':
(u"If U\N{RIGHTWARDS ARROW}{{{0}}} and U\N{RIGHTWARDS ARROW}{1}"
" then P({1}|{0},{2},U) = P({1}|{0},{2})").format(
",".join(treatment_name), outcome_name,
",".join(common_causes))
}
estimand = {'estimand': sym_effect, 'assumptions': sym_assumptions}
return estimand
def construct_frontdoor_estimand(self, estimand_type, treatment_name,
outcome_name, frontdoor_variables_names):
# TODO: support multivariate treatments better.
expr = None
outcome_name = outcome_name[0]
sym_outcome = spstats.Normal(outcome_name, 0, 1)
sym_treatment_symbols = [spstats.Normal(t, 0, 1) for t in treatment_name]
sym_treatment = sp.Array(sym_treatment_symbols)
sym_frontdoor_symbols = [sp.Symbol(inst) for inst in frontdoor_variables_names]
sym_frontdoor = sp.Array(sym_frontdoor_symbols) # ",".join(instrument_names))
sym_outcome_derivative = sp.Derivative(sym_outcome, sym_frontdoor)
sym_treatment_derivative = sp.Derivative(sym_frontdoor, sym_treatment)
sym_effect = spstats.Expectation(sym_treatment_derivative * sym_outcome_derivative)
sym_assumptions = {
"Full-mediation": (
"{2} intercepts (blocks) all directed paths from {0} to {1}."
).format(",".join(treatment_name), ",".join(outcome_name), ",".join(frontdoor_variables_names)),
"First-stage-unconfoundedness": (
u"If U\N{RIGHTWARDS ARROW}{{{0}}} and U\N{RIGHTWARDS ARROW}{{{1}}}"
" then P({1}|{0},U) = P({1}|{0})"
).format(",".join(treatment_name), ",".join(frontdoor_variables_names)),
"Second-stage-unconfoundedness": (
u"If U\N{RIGHTWARDS ARROW}{{{2}}} and U\N{RIGHTWARDS ARROW}{1}"
" then P({1}|{2}, {0}, U) = P({1}|{2}, {0})"
).format(",".join(treatment_name), outcome_name, ",".join(frontdoor_variables_names))
}
estimand = {
'estimand': sym_effect,
'assumptions': sym_assumptions
}
return estimand
