[ENH] add feature scaling support for EncoderDecoderDataModule

docs/source/tutorials/ptf_V2_example.ipynb

@@ -493,7 +493,7 @@
     },
     {
       "cell_type": "code",
-      "execution_count": 10,
+      "execution_count": null,
       "metadata": {
         "colab": {
           "base_uri": "https://localhost:8080/",

pytorch_forecasting/data/data_module.py

@@ -339,6 +339,81 @@ def _preprocess_data(self, series_idx: torch.Tensor) -> list[dict[str, Any]]:
             else torch.zeros((features.shape[0], 0))
         )
 
+        if self._scalers and self.continuous_indices:
+            for i, orig_idx in enumerate(self.continuous_indices):
+                col_name = self.time_series_metadata["cols"]["x"][orig_idx]
+                if col_name in self._scalers:
+                    scaler = self._scalers[col_name]
+                    feature_data = continuous[:, i]
+                    try:
+                        if isinstance(scaler, (TorchNormalizer, EncoderNormalizer)):
+                            continuous[:, i] = scaler.transform(feature_data)
+                        elif isinstance(scaler, (StandardScaler, RobustScaler)):
+                            # if scaler is a sklearn scaler, we need to
+                            # input numpy np.array
+                            requires_grad = feature_data.requires_grad
+                            device = feature_data.device
+                            feature_data_np = (
+                                feature_data.cpu().detach().numpy().reshape(-1, 1)
+                            )  # noqa: E501
+                            scaled_feature_np = scaler.transform(feature_data_np)
+                            scaled_tensor = torch.from_numpy(
+                                scaled_feature_np.flatten()
+                            ).to(device)
+                            if requires_grad:
+                                scaled_tensor = scaled_tensor.requires_grad_(True)
+                            continuous[:, i] = scaled_tensor
+                    except Exception as e:
+                        import warnings
+
+                        warnings.warn(
+                            f"Failed to transform feature '{col_name}' with scaler: {e}. "  # noqa: E501
+                            f"Using unscaled values.",
+                            UserWarning,
+                        )
+                        continue
+
+        if self._target_normalizer is not None:
+            try:
+                if isinstance(
+                    self._target_normalizer, (TorchNormalizer, EncoderNormalizer)
+                ):
+                    # automatically handle multiple targets.
+                    target = self._target_normalizer.transform(target)
+                elif isinstance(
+                    self._target_normalizer, (StandardScaler, RobustScaler)
+                ):
+                    requires_grad = target.requires_grad
+                    device = target.device
+                    if target.ndim == 2:  # (seq_len, n_targets)
+                        target_scaled = []
+                        for i in range(target.shape[1]):
+                            target_np = (
+                                target[:, i].detach().cpu().numpy().reshape(-1, 1)
+                            )  # noqa: E501
+                            scaled = self._target_normalizer.transform(target_np)
+                            scaled_tensor = torch.from_numpy(scaled.flatten()).to(
+                                device
+                            )  # noqa: E501
+                            if requires_grad:
+                                scaled_tensor = scaled_tensor.requires_grad_(True)
+                            target_scaled.append(scaled_tensor)
+                        target = torch.stack(target_scaled, dim=1)
+                    else:
+                        target_np = target.detach().cpu().numpy().reshape(-1, 1)
+                        target_scaled = self._target_normalizer.transform(target_np)
+                        target = torch.from_numpy(target_scaled.flatten()).to(device)
+                        if requires_grad:
+                            target = target.requires_grad_(True)
+            except Exception as e:
+                import warnings
+
+                warnings.warn(
+                    f"Failed to transform target with scaler: {e}. "  # noqa: E501
+                    f"Using unscaled values.",
+                    UserWarning,
+                )
+
         return {
             "features": {"categorical": categorical, "continuous": continuous},
             "target": target,
@@ -623,6 +698,52 @@ def _create_windows(self, indices: torch.Tensor) -> list[tuple[int, int, int, in
 
         return windows
 
+    def _fit_scalers(self, train_indices: torch.Tensor):
+        """Fit scaler on the training dataset.
+
+        Parameters
+        ----------
+        train_indices : torch.Tensor
+            Indices of the training time series in `time_series_dataset`.
+        """
+
+        train_targets = []
+        train_features = []
+
+        for series_idx in train_indices:
+            sample = self.time_series_dataset[series_idx.item()]
+            target = sample["y"]
+            features = sample["x"]
+
+            train_targets.append(target)
+            train_features.append(features)
+
+        train_targets = torch.cat(train_targets, dim=0)
+        train_features = torch.cat(train_features, dim=0)
+
+        if self._target_normalizer is not None:
+            if isinstance(
+                self._target_normalizer, (TorchNormalizer, EncoderNormalizer)
+            ):
+                self._target_normalizer.fit(train_targets)
+            elif isinstance(self._target_normalizer, (StandardScaler, RobustScaler)):
+                target_np = train_targets.numpy()
+                if target_np.ndim == 1:
+                    target_np = target_np.reshape(-1, 1)
+                self._target_normalizer.fit(target_np)
+
+        if self._scalers and self.continuous_indices:
+            for i, orig_idx in enumerate(self.continuous_indices):
+                col_name = self.time_series_metadata["cols"]["x"][orig_idx]
+                if col_name in self._scalers:
+                    scaler = self._scalers[col_name]
+                    feature_data = train_features[:, orig_idx]
+
+                    if isinstance(scaler, (StandardScaler, RobustScaler)):
+                        feature_data = feature_data.numpy().reshape(-1, 1)
+
+                    scaler.fit(feature_data)
+
     def setup(self, stage: Optional[str] = None):
         """Prepare the datasets for training, validation, testing, or prediction.
 
@@ -647,6 +768,9 @@ def setup(self, stage: Optional[str] = None):
         ]
         self._test_indices = self._split_indices[self._train_size + self._val_size :]
 
+        if (stage is None or stage == "fit") and len(self._train_indices) > 0:
+            self._fit_scalers(self._train_indices)
+
         if stage is None or stage == "fit":
             if not hasattr(self, "train_dataset") or not hasattr(self, "val_dataset"):
                 self.train_windows = self._create_windows(self._train_indices)