Book Image

Python Feature Engineering Cookbook - Second Edition

By : Soledad Galli
Book Image

Python Feature Engineering Cookbook - Second Edition

By: Soledad Galli

Overview of this book

Feature engineering, the process of transforming variables and creating features, albeit time-consuming, ensures that your machine learning models perform seamlessly. This second edition of Python Feature Engineering Cookbook will take the struggle out of feature engineering by showing you how to use open source Python libraries to accelerate the process via a plethora of practical, hands-on recipes. This updated edition begins by addressing fundamental data challenges such as missing data and categorical values, before moving on to strategies for dealing with skewed distributions and outliers. The concluding chapters show you how to develop new features from various types of data, including text, time series, and relational databases. With the help of numerous open source Python libraries, you'll learn how to implement each feature engineering method in a performant, reproducible, and elegant manner. By the end of this Python book, you will have the tools and expertise needed to confidently build end-to-end and reproducible feature engineering pipelines that can be deployed into production.
Table of Contents (14 chapters)

Estimating missing data with nearest neighbors

In imputation with K-Nearest Neighbors (KNN), missing values are replaced with the mean value from their k closest neighbors. The neighbors of each observation are found utilizing distances like the Euclidean distance, and the replacement value can be estimated as the mean or weighted mean of the neighbor’s value, where further neighbors have less influence on the replacement value. In this recipe, we will perform KNN imputation using scikit-learn.

How to do it...

To proceed with the recipe, let’s import the required libraries and prepare the data:

  1. Let’s import the required libraries, classes, and functions:
    import matplotlib.pyplot as plt
    import pandas as pd
    from sklearn.model_selection import train_test_split
    from sklearn.impute import KNNImputer
  2. Let’s load the dataset that we prepared in the Technical requirements section only with some numerical variables:
    variables = ["A2", &quot...