from evalml.pipelines.components.transformers import Transformer from evalml.pipelines.components.transformers.imputers import SimpleImputer from evalml.utils.gen_utils import ( _convert_to_woodwork_structure, _convert_woodwork_types_wrapper ) [docs]class Imputer(Transformer): """Imputes missing data according to a specified imputation strategy.""" name = "Imputer" hyperparameter_ranges = { "categorical_impute_strategy": ["most_frequent"], "numeric_impute_strategy": ["mean", "median", "most_frequent"] } _valid_categorical_impute_strategies = set(["most_frequent", "constant"]) _valid_numeric_impute_strategies = set(["mean", "median", "most_frequent", "constant"]) [docs] def __init__(self, categorical_impute_strategy="most_frequent", categorical_fill_value=None, numeric_impute_strategy="mean", numeric_fill_value=None, random_state=0, **kwargs): """Initalizes an transformer that imputes missing data according to the specified imputation strategy." Arguments: categorical_impute_strategy (string): Impute strategy to use for string, object, boolean, categorical dtypes. Valid values include "most_frequent" and "constant". numeric_impute_strategy (string): Impute strategy to use for numeric columns. Valid values include "mean", "median", "most_frequent", and "constant". categorical_fill_value (string): When categorical_impute_strategy == "constant", fill_value is used to replace missing data. The default value of None will fill with the string "missing_value". numeric_fill_value (int, float): When numeric_impute_strategy == "constant", fill_value is used to replace missing data. The default value of None will fill with 0. """ if categorical_impute_strategy not in self._valid_categorical_impute_strategies: raise ValueError(f"{categorical_impute_strategy} is an invalid parameter. Valid categorical impute strategies are {', '.join(self._valid_numeric_impute_strategies)}") elif numeric_impute_strategy not in self._valid_numeric_impute_strategies: raise ValueError(f"{numeric_impute_strategy} is an invalid parameter. Valid impute strategies are {', '.join(self._valid_numeric_impute_strategies)}") parameters = {"categorical_impute_strategy": categorical_impute_strategy, "numeric_impute_strategy": numeric_impute_strategy, "categorical_fill_value": categorical_fill_value, "numeric_fill_value": numeric_fill_value} parameters.update(kwargs) self._categorical_imputer = SimpleImputer(impute_strategy=categorical_impute_strategy, fill_value=categorical_fill_value, **kwargs) self._numeric_imputer = SimpleImputer(impute_strategy=numeric_impute_strategy, fill_value=numeric_fill_value, **kwargs) self._all_null_cols = None self._numeric_cols = None self._categorical_cols = None super().__init__(parameters=parameters, component_obj=None, random_state=random_state) [docs] def fit(self, X, y=None): """Fits imputer to data. 'None' values are converted to np.nan before imputation and are treated as the same. Arguments: X (ww.DataTable, pd.DataFrame or np.ndarray): The input training data of shape [n_samples, n_features] y (ww.DataColumn, pd.Series, optional): The target training data of length [n_samples] Returns: self """ X = _convert_to_woodwork_structure(X) cat_cols = list(X.select('category').columns) numeric_cols = list(X.select('numeric').columns) X = _convert_woodwork_types_wrapper(X.to_dataframe()) self._all_null_cols = set(X.columns) - set(X.dropna(axis=1, how='all').columns) X_copy = X.copy() X_null_dropped = X_copy.drop(self._all_null_cols, axis=1, errors='ignore') X_numerics = X_null_dropped[[col for col in numeric_cols if col not in self._all_null_cols]] if len(X_numerics.columns) > 0: self._numeric_imputer.fit(X_numerics, y) self._numeric_cols = X_numerics.columns X_categorical = X_null_dropped[[col for col in cat_cols if col not in self._all_null_cols]] if len(X_categorical.columns) > 0: self._categorical_imputer.fit(X_categorical, y) self._categorical_cols = X_categorical.columns return self [docs] def transform(self, X, y=None): """Transforms data X by imputing missing values. 'None' values are converted to np.nan before imputation and are treated as the same. Arguments: X (ww.DataTable, pd.DataFrame): Data to transform y (ww.DataColumn, pd.Series, optional): Ignored. Returns: ww.DataTable: Transformed X """ X = _convert_to_woodwork_structure(X) X = _convert_woodwork_types_wrapper(X.to_dataframe()) X_null_dropped = X.copy() X_null_dropped.drop(self._all_null_cols, inplace=True, axis=1, errors='ignore') if X_null_dropped.empty: return _convert_to_woodwork_structure(X_null_dropped) if self._numeric_cols is not None and len(self._numeric_cols) > 0: X_numeric = X_null_dropped[self._numeric_cols] imputed = self._numeric_imputer.transform(X_numeric).to_dataframe() X_null_dropped[X_numeric.columns] = imputed if self._categorical_cols is not None and len(self._categorical_cols) > 0: X_categorical = X_null_dropped[self._categorical_cols] imputed = self._categorical_imputer.transform(X_categorical).to_dataframe() X_null_dropped[X_categorical.columns] = imputed X_null_dropped = _convert_to_woodwork_structure(X_null_dropped) return X_null_dropped