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Add "ri" resampling method to Romano-Wolf procedure, #514

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Jun 19, 2024
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2 changes: 1 addition & 1 deletion .github/workflows/release-drafter.yml
Original file line number Diff line number Diff line change
Expand Up @@ -21,4 +21,4 @@ jobs:
config-name: release-config.yml
disable-autolabeler: true
env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
46 changes: 34 additions & 12 deletions pyfixest/estimation/multcomp.py
Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,11 @@


def rwolf(
models: list[Union[Feols, Fepois]], param: str, reps: int, seed: int
models: list[Union[Feols, Fepois]],
param: str,
reps: int,
seed: int,
sampling_method: str = "wild-bootstrap",
) -> pd.DataFrame:
"""
Compute Romano-Wolf adjusted p-values for multiple hypothesis testing.
Expand All @@ -86,6 +90,10 @@
The number of bootstrap replications.
seed : int
The seed for the random number generator.
sampling_method : str
Sampling method for computing resampled statistics.
Users can choose either bootstrap('wild-bootstrap')
or randomization inference('ri')

Returns
-------
Expand Down Expand Up @@ -142,34 +150,48 @@
for i in range(S):
model = models[i]

wildboot_res_df, bootstrapped_t_stats = model.wildboottest(
param=param,
reps=reps,
return_bootstrapped_t_stats=True,
seed=seed, # all S iterations require the same bootstrap samples, hence seed needs to be reset
)
t_stats[i] = wildboot_res_df["t value"]
boot_t_stats[:, i] = bootstrapped_t_stats
if sampling_method == "wild-bootstrap":
wildboot_res_df, bootstrapped_t_stats = model.wildboottest(
param=param,
reps=reps,
return_bootstrapped_t_stats=True,
seed=seed, # all S iterations require the same bootstrap samples, hence seed needs to be reset
)

t_stats[i] = wildboot_res_df["t value"]
boot_t_stats[:, i] = bootstrapped_t_stats

elif sampling_method == "ri":
model.ritest(
resampvar=param,
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reps=reps,
type="randomization-t",
store_ritest_statistics=True,
)

t_stats[i] = model._ritest_sample_stat
boot_t_stats[:, i] = model._ritest_statistics
else:
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raise ValueError("Invalid sampling method specified")

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pval = _get_rwolf_pval(t_stats, boot_t_stats)

all_model_stats.loc["RW Pr(>|t|)"] = pval
all_model_stats.columns = pd.Index([f"est{i}" for i, _ in enumerate(models)])

return all_model_stats


def _get_rwolf_pval(t_stats, boot_t_stats):
"""
Compute Romano-Wolf adjusted p-values based on bootstrapped t-statistics.
Compute Romano-Wolf adjusted p-values based on bootstrapped(or "ri") t-statistics.

Parameters
----------
t_stats (np.ndarray): A vector of length S - where S is the number of
tested hypotheses - containing the original,
non-bootstrappe t-statisics.
boot_t_stats (np.ndarray): A (B x S) matrix containing the
bootstrapped t-statistics.
bootstrapped(or "ri") t-statistics.

Returns
-------
Expand Down
44 changes: 44 additions & 0 deletions tests/test_multcomp.py
Original file line number Diff line number Diff line change
Expand Up @@ -143,3 +143,47 @@ def test_stepwise_function():
stepwise_r = wildrwolf.get_rwolf_pval(t_stat, t_boot)

np.testing.assert_allclose(stepwise_py, stepwise_r)


# Import data from pyfixest


@pytest.mark.parametrize("seed", [1000, 2000, 3000])
@pytest.mark.parametrize("reps", [999, 1999])
def test_sampling_scheme(seed, reps):
# Compare RW adjusted p-values from RI and WB resampling methods
# The p-values should be "largely" similar regardless of resampling methods

data = get_data().dropna()
rng = np.random.default_rng(seed)

# Perturb covariates(not treatment variable)
data["Y2"] = data["Y"] * rng.normal(0.2, 1, size=len(data))
data["X2"] = rng.normal(size=len(data))

fit1 = feols("Y ~ X1 + X2", data=data)
fit2 = feols("Y ~ X1 + X2 + Y2", data=data)

# Run rwolf with "ri" sampling method
rwolf_df_ri = rwolf([fit1, fit2], "X1", reps=reps, seed=seed, sampling_method="ri")

ri_pval = rwolf_df_ri["est1"]["RW Pr(>|t|)"]

# Run rwolf with "wild-bootstrap" sampling method
rwolf_df_wb = rwolf(
[fit1, fit2], "X1", reps=reps, seed=seed, sampling_method="wild-bootstrap"
)

wb_pval = rwolf_df_wb["est1"]["RW Pr(>|t|)"]

# Calculate percentage difference in p-values
percent_diff = 100 * (wb_pval - ri_pval) / ri_pval

print(
f"Percentage difference in p-values (seed={seed}, reps={reps}): {percent_diff}"
)

# Assert that the percentage difference is within an acceptable range
assert (
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np.abs(percent_diff) < 1.0
), f"Percentage difference is too large: {percent_diff}%"