scikit-learn · OmarManzoor · Feb 13, 2024 · Jan 19, 2024 · Jan 19, 2024 · Jan 26, 2024
diff --git a/doc/metadata_routing.rst b/doc/metadata_routing.rst
@@ -252,6 +252,7 @@ Meta-estimators and functions supporting metadata routing:
 - :class:`sklearn.calibration.CalibratedClassifierCV`
 - :class:`sklearn.compose.ColumnTransformer`
 - :class:`sklearn.feature_selection.SelectFromModel`
+- :class:`sklearn.impute.IterativeImputer`
 - :class:`sklearn.linear_model.ElasticNetCV`
 - :class:`sklearn.linear_model.LarsCV`
 - :class:`sklearn.linear_model.LassoCV`
@@ -291,7 +292,6 @@ Meta-estimators and tools not supporting metadata routing yet:
 - :class:`sklearn.feature_selection.RFE`
 - :class:`sklearn.feature_selection.RFECV`
 - :class:`sklearn.feature_selection.SequentialFeatureSelector`
-- :class:`sklearn.impute.IterativeImputer`
 - :class:`sklearn.linear_model.RANSACRegressor`
 - :class:`sklearn.linear_model.RidgeClassifierCV`
 - :class:`sklearn.linear_model.RidgeCV`

diff --git a/doc/whats_new/v1.5.rst b/doc/whats_new/v1.5.rst
@@ -32,6 +32,17 @@ Meson is now supported as a build backend, see :ref:`Building with Meson
 
 TODO Fill more details before the 1.5 release, when the Meson story has settled down.
 
+Metadata Routing
+----------------
+
+The following models now support metadata routing in one or more or their
+methods. Refer to the :ref:`Metadata Routing User Guide <metadata_routing>` for
+more details.
+
+- |Feature| :class:`impute.IterativeImputer` now supports metadata routing in
+  its `fit` method. :pr:`28187` by :user:`Stefanie Senger <StefanieSenger>`.
+
+
 Changelog
 ---------
 

diff --git a/sklearn/feature_selection/_from_model.py b/sklearn/feature_selection/_from_model.py
@@ -343,12 +343,12 @@ def fit(self, X, y=None, **fit_params):
         **fit_params : dict
             - If `enable_metadata_routing=False` (default):
 
-                Parameters directly passed to the `partial_fit` method of the
+                Parameters directly passed to the `fit` method of the
                 sub-estimator. They are ignored if `prefit=True`.
 
             - If `enable_metadata_routing=True`:
 
-                Parameters safely routed to the `partial_fit` method of the
+                Parameters safely routed to the `fit` method of the
                 sub-estimator. They are ignored if `prefit=True`.
 
                 .. versionchanged:: 1.4

diff --git a/sklearn/impute/_iterative.py b/sklearn/impute/_iterative.py
@@ -18,7 +18,12 @@
 )
 from ..utils._mask import _get_mask
 from ..utils._param_validation import HasMethods, Interval, StrOptions
-from ..utils.metadata_routing import _RoutingNotSupportedMixin
+from ..utils.metadata_routing import (
+    MetadataRouter,
+    MethodMapping,
+    _raise_for_params,
+    process_routing,
+)
 from ..utils.validation import FLOAT_DTYPES, _check_feature_names_in, check_is_fitted
 from ._base import SimpleImputer, _BaseImputer, _check_inputs_dtype
 
@@ -47,7 +52,7 @@ def _assign_where(X1, X2, cond):
         X1[cond] = X2[cond]
 
 
-class IterativeImputer(_RoutingNotSupportedMixin, _BaseImputer):
+class IterativeImputer(_BaseImputer):
     """Multivariate imputer that estimates each feature from all the others.
 
     A strategy for imputing missing values by modeling each feature with
@@ -349,6 +354,7 @@ def _impute_one_feature(
         neighbor_feat_idx,
         estimator=None,
         fit_mode=True,
+        params=None,
     ):
         """Impute a single feature from the others provided.
 
@@ -380,6 +386,9 @@ def _impute_one_feature(
         fit_mode : boolean, default=True
             Whether to fit and predict with the estimator or just predict.
 
+        params : dict
+            Additional params routed to the individual estimator.
+
         Returns
         -------
         X_filled : ndarray
@@ -410,7 +419,7 @@ def _impute_one_feature(
                 ~missing_row_mask,
                 axis=0,
             )
-            estimator.fit(X_train, y_train)
+            estimator.fit(X_train, y_train, **params)
 
         # if no missing values, don't predict
         if np.sum(missing_row_mask) == 0:
@@ -685,7 +694,7 @@ def _validate_limit(limit, limit_type, n_features):
         # IterativeImputer.estimator is not validated yet
         prefer_skip_nested_validation=False
     )
-    def fit_transform(self, X, y=None):
+    def fit_transform(self, X, y=None, **params):
         """Fit the imputer on `X` and return the transformed `X`.
 
         Parameters
@@ -697,11 +706,29 @@ def fit_transform(self, X, y=None):
         y : Ignored
             Not used, present for API consistency by convention.
 
+        **params : dict
+            Parameters routed to the `fit` method of the sub-estimator via the
+            metadata routing API.
+
+            .. versionadded:: 1.5
+              Only available if
+              `sklearn.set_config(enable_metadata_routing=True)` is set. See
+              :ref:`Metadata Routing User Guide <metadata_routing>` for more
+              details.
+
         Returns
         -------
         Xt : array-like, shape (n_samples, n_features)
             The imputed input data.
         """
+        _raise_for_params(params, self, "fit")
+
+        routed_params = process_routing(
+            self,
+            "fit",
+            **params,
+        )
+
         self.random_state_ = getattr(
             self, "random_state_", check_random_state(self.random_state)
         )
@@ -728,7 +755,7 @@ def fit_transform(self, X, y=None):
             self.n_iter_ = 0
             return super()._concatenate_indicator(Xt, X_indicator)
 
-        # Edge case: a single feature. We return the initial ...
+        # Edge case: a single feature, we return the initial imputation.
         if Xt.shape[1] == 1:
             self.n_iter_ = 0
             return super()._concatenate_indicator(Xt, X_indicator)
@@ -770,6 +797,7 @@ def fit_transform(self, X, y=None):
                     neighbor_feat_idx,
                     estimator=None,
                     fit_mode=True,
+                    params=routed_params.estimator.fit,
                 )
                 estimator_triplet = _ImputerTriplet(
                     feat_idx, neighbor_feat_idx, estimator
@@ -860,7 +888,7 @@ def transform(self, X):
 
         return super()._concatenate_indicator(Xt, X_indicator)
 
-    def fit(self, X, y=None):
+    def fit(self, X, y=None, **fit_params):
         """Fit the imputer on `X` and return self.
 
         Parameters
@@ -872,12 +900,22 @@ def fit(self, X, y=None):
         y : Ignored
             Not used, present for API consistency by convention.
 
+        **fit_params : dict
+            Parameters routed to the `fit` method of the sub-estimator via the
+            metadata routing API.
+
+            .. versionadded:: 1.5
+              Only available if
+              `sklearn.set_config(enable_metadata_routing=True)` is set. See
+              :ref:`Metadata Routing User Guide <metadata_routing>` for more
+              details.
+
         Returns
         -------
         self : object
             Fitted estimator.
         """
-        self.fit_transform(X)
+        self.fit_transform(X, **fit_params)
         return self
 
     def get_feature_names_out(self, input_features=None):
@@ -904,3 +942,23 @@ def get_feature_names_out(self, input_features=None):
         input_features = _check_feature_names_in(self, input_features)
         names = self.initial_imputer_.get_feature_names_out(input_features)
         return self._concatenate_indicator_feature_names_out(names, input_features)
+
+    def get_metadata_routing(self):
+        """Get metadata routing of this object.
+
+        Please check :ref:`User Guide <metadata_routing>` on how the routing
+        mechanism works.
+
+        .. versionadded:: 1.5
+
+        Returns
+        -------
+        routing : MetadataRouter
+            A :class:`~sklearn.utils.metadata_routing.MetadataRouter` encapsulating
+            routing information.
+        """
+        router = MetadataRouter(owner=self.__class__.__name__).add(
+            estimator=self.estimator,
+            method_mapping=MethodMapping().add(callee="fit", caller="fit"),
+        )
+        return router
diff --git a/sklearn/tests/test_metaestimators_metadata_routing.py b/sklearn/tests/test_metaestimators_metadata_routing.py
@@ -289,6 +289,15 @@ def enable_slep006():
         "cv_name": "cv",
         "cv_routing_methods": ["fit"],
     },
+    {
+        "metaestimator": IterativeImputer,
+        "estimator_name": "estimator",
+        "estimator": ConsumingRegressor,
+        "init_args": {"skip_complete": False},
+        "X": X,
+        "y": y,
+        "estimator_routing_methods": ["fit"],
+    },
 ]
 """List containing all metaestimators to be tested and their settings
 
@@ -331,7 +340,6 @@ def enable_slep006():
     BaggingRegressor(),
     FeatureUnion([]),
     GraphicalLassoCV(),
-    IterativeImputer(),
     RANSACRegressor(),
     RFE(ConsumingClassifier()),
     RFECV(ConsumingClassifier()),