Merge pull request #39 from igerber/claude/refactor-estimators-n3DzQ

Author: igerber

CLAUDE.md

@@ -37,8 +37,13 @@ mypy diff_diff
 
 - **`diff_diff/estimators.py`** - Core estimator classes implementing DiD methods:
   - `DifferenceInDifferences` - Basic 2x2 DiD with formula or column-name interface
-  - `TwoWayFixedEffects` - Panel DiD with unit and time fixed effects (within-transformation)
   - `MultiPeriodDiD` - Event-study style DiD with period-specific treatment effects
+  - Re-exports `TwoWayFixedEffects` and `SyntheticDiD` for backward compatibility
+
+- **`diff_diff/twfe.py`** - Two-Way Fixed Effects estimator:
+  - `TwoWayFixedEffects` - Panel DiD with unit and time fixed effects (within-transformation)
+
+- **`diff_diff/synthetic_did.py`** - Synthetic DiD estimator:
   - `SyntheticDiD` - Synthetic control combined with DiD (Arkhangelsky et al. 2021)
 
 - **`diff_diff/staggered.py`** - Staggered adoption DiD estimators:

README.md

@@ -539,7 +539,7 @@ Works with `DifferenceInDifferences` and `TwoWayFixedEffects` estimators.
 ### Two-Way Fixed Effects (Panel Data)
 
 ```python
-from diff_diff.estimators import TwoWayFixedEffects
+from diff_diff import TwoWayFixedEffects
 
 twfe = TwoWayFixedEffects()
 results = twfe.fit(

TODO.md

@@ -78,16 +78,20 @@ Current line counts (target: < 1000 lines per module):
 | File | Lines | Status |
 |------|-------|--------|
 | `staggered.py` | 1822 | Consider splitting |
-| `estimators.py` | 1812 | Consider splitting |
+| `estimators.py` | ~975 | OK (refactored) |
+| `twfe.py` | ~355 | OK (new) |
+| `synthetic_did.py` | ~540 | OK (new) |
 | `honest_did.py` | 1491 | Acceptable |
 | `utils.py` | 1350 | Acceptable |
 | `power.py` | 1350 | Acceptable |
 | `prep.py` | 1338 | Acceptable |
 | `visualization.py` | 1388 | Acceptable |
 | `bacon.py` | 1027 | OK |
 
+**Completed splits:**
+- ~~`estimators.py` → `twfe.py`, `synthetic_did.py` (keep base classes in estimators.py)~~ - Done in 1.0.2
+
 **Potential splits:**
-- `estimators.py` → `twfe.py`, `synthetic_did.py` (keep base classes in estimators.py)
 - `staggered.py` → `staggered_bootstrap.py` (move bootstrap logic)
 
 ---

diff_diff/__init__.py

@@ -85,7 +85,7 @@
     plot_sensitivity,
 )
 
-__version__ = "1.0.0"
+__version__ = "1.0.2"
 __all__ = [
     # Estimators
     "DifferenceInDifferences",