[Repo Assist] fix: handle list-form treatment_variable in estimate_effect_naive

[github-actions]

🤖 This PR was created by Repo Assist, an automated AI assistant. Please review carefully before merging.

Closes #416

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Root Cause

estimate_effect_naive() in CausalEstimator had two related bugs:

1. List indexing: self._target_estimand.treatment_variable and outcome_variable are always lists (returned by parse_state()). The old code did data[list_of_names] == 1, which produces a 2D boolean DataFrame. Using that as a .loc index key raises:

   ValueError: Cannot index with multidimensional key
   

2. Hardcoded treatment/control values: The method used == 1 / == 0, ignoring the actual treatment_value / control_value that the caller passed to estimate_effect(). For non-binary or custom-valued treatments this returned a wrong or empty estimate.

Fix

• Extract the scalar variable name from the list (treatment_variable[0]), falling back gracefully if already a scalar.
• Use self._treatment_value / self._control_value (set by update_input() / estimate_effect()) instead of the hardcoded constants. Falls back to 1/0 if not yet set.

The fix is surgical — 4 changed lines in estimate_effect_naive() only.

Test Status

⚠️ The test runner environment did not have the required Python packages installed (pandas, numpy, etc.), preventing automated test execution. This is an infrastructure limitation of this run, not a code issue.

Code quality checks:

• ✅ black --check passed (no formatting changes needed)
• ✅ No new flake8 violations introduced (pre-existing E501 violations in the file are unrelated)

Manual verification: The logic was verified by code inspection:

• treatment_variable[0] correctly extracts the single column name
• data[scalar_name] == value produces a 1D boolean Series (correct for .loc)
• self._treatment_value is set in update_input() which is called by all concrete estimators' estimate_effect() before evaluate_effect_strength is called

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[Copilot]

Pull request overview

Note

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Fixes estimate_effect_naive() to correctly handle list-form treatment_variable / outcome_variable and to respect caller-provided treatment/control values (per #416).

Changes:

• Extract scalar treatment/outcome column names from list-form variables to avoid 2D boolean indexing.
• Use self._treatment_value / self._control_value (with 1/0 fallback) instead of hardcoded values.

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[github-actions]

🤖 This is an automated note from Repo Assist.

This PR is superseded by #1553 and can be safely closed.

PR #1553 ("[Repo Assist] fix: estimate_effect_naive handles list treatment_variable and uses actual treatment/control values") is a newer, more comprehensive fix for issue #416 that:

• Extracts the scalar column name from the list properly
• Uses self._treatment_value / self._control_value instead of the hardcoded 1/0
• Adds proper regression tests

Maintainers: please close this PR and review #1553 instead.

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