PowerTransformer

API Reference

class feature_engine.variable_transformers.PowerTransformer(exp=0.5, variables=None)[source]

The PowerTransformer() applies power or exponential transformations to numerical variables.

The PowerTransformer() works only with numerical variables.

A list of variables can be passed as an argument. Alternatively, the transformer will automatically select and transform all numerical variables.

Parameters
  • variables (list, default=None) – The list of numerical variables that will be transformed. If None, the transformer will automatically find and select all numerical variables.

  • exp (float or int, default=0.5) – The power (or exponent).

fit(X, y=None)[source]
Parameters
  • X (pandas dataframe of shape = [n_samples, n_features]) – The training input samples. Can be the entire dataframe, not just the variables to transform.

  • y (None) – y is not needed in this transformer. You can pass y or None.

transform(X)[source]

Applies the power transformation to the variables.

Parameters

X (pandas dataframe of shape = [n_samples, n_features]) – The data to be transformed.

Returns

X_transformed – The dataframe with the power transformed variables.

Return type

pandas dataframe of shape = [n_samples, n_features]

Example Use

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from sklearn.model_selection import train_test_split

from feature_engine import variable_transformers as vt

# Load dataset
data = data = pd.read_csv('houseprice.csv')

# Separate into train and test sets
X_train, X_test, y_train, y_test =  train_test_split(
            data.drop(['Id', 'SalePrice'], axis=1),
            data['SalePrice'], test_size=0.3, random_state=0)

# set up the variable transformer
tf = vt.PowerTransformer(variables = ['LotArea', 'GrLivArea'], exp=0.5)

# fit the transformer
tf.fit(X_train)

# transform the data
train_t= tf.transform(X_train)
test_t= tf.transform(X_test)

# un-transformed variable
X_train['LotArea'].hist(bins=50)
../_images/lotarearaw.png
# transformed variable
train_t['LotArea'].hist(bins=50)
../_images/lotareapower.png