Source code for evalml.pipelines.components.transformers.imputers.simple_imputer

import numpy as np
import pandas as pd
from sklearn.impute import SimpleImputer as SkImputer

from evalml.pipelines.components.transformers import Transformer


[docs]class SimpleImputer(Transformer): """Imputes missing data according to a specified imputation strategy.""" name = 'Simple Imputer' hyperparameter_ranges = {"impute_strategy": ["mean", "median", "most_frequent"]}
[docs] def __init__(self, impute_strategy="most_frequent", fill_value=None, random_state=0, **kwargs): """Initalizes an transformer that imputes missing data according to the specified imputation strategy." Arguments: impute_strategy (string): Impute strategy to use. Valid values include "mean", "median", "most_frequent", "constant" for numerical data, and "most_frequent", "constant" for object data types. fill_value (string): When impute_strategy == "constant", fill_value is used to replace missing data. Defaults to 0 when imputing numerical data and "missing_value" for strings or object data types. """ parameters = {"impute_strategy": impute_strategy, "fill_value": fill_value} parameters.update(kwargs) imputer = SkImputer(strategy=impute_strategy, fill_value=fill_value, **kwargs) self._all_null_cols = None super().__init__(parameters=parameters, component_obj=imputer, 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 (pd.DataFrame or np.array): the input training data of shape [n_samples, n_features] y (pd.Series, optional): the target training data of length [n_samples] Returns: self """ if not isinstance(X, pd.DataFrame): X = pd.DataFrame(X) # Convert None to np.nan, since None cannot be properly handled X = X.fillna(value=np.nan) self._component_obj.fit(X, y) self._all_null_cols = set(X.columns) - set(X.dropna(axis=1, how='all').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 (pd.DataFrame): Data to transform y (pd.Series, optional): Ignored. Returns: pd.DataFrame: Transformed X """ if not isinstance(X, pd.DataFrame): X = pd.DataFrame(X) # Convert None to np.nan, since None cannot be properly handled X = X.fillna(value=np.nan) X_null_dropped = X.copy() X_null_dropped.drop(self._all_null_cols, axis=1, errors='ignore', inplace=True) category_cols = X_null_dropped.select_dtypes(include=['category']).columns X_t = self._component_obj.transform(X) if X_null_dropped.empty: return pd.DataFrame(X_t, columns=X_null_dropped.columns) X_t = pd.DataFrame(X_t, columns=X_null_dropped.columns) if len(category_cols) > 0: X_t[category_cols] = X_t[category_cols].astype('category') return X_t
[docs] def fit_transform(self, X, y=None): """Fits on X and transforms X Arguments: X (pd.DataFrame): Data to fit and transform y (pd. DataFrame): Target data. Returns: pd.DataFrame: Transformed X """ return self.fit(X, y).transform(X, y)