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)

Performing Feature Scaling

Many machine learning algorithms are sensitive to the scale of the features. In particular, the coefficients of linear models depend on the scale of the feature; that is, changing the feature scale will change the coefficient’s value. In linear models, as well as and algorithms that depend on distance calculations, such as clustering and principal component analysis, features with bigger value ranges tend to dominate over features with smaller ranges. Therefore, having features within a similar scale allows us to compare feature importance and also helps algorithms converge faster, thus improving performance and training times.

Scaling techniques will divide the variables by some constant; therefore, it is important to highlight that no matter the scaling method, the shape of the variable distribution does not change. If what you want is to change the distribution shape, check out Chapter 3, Transforming Numerical Variables.

In this chapter,...