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)

Creating features with aggregation primitives

Throughout this chapter, we’ve created features automatically by transforming existing variables into new features. For example, we extracted date and time parts from datetime variables, we counted the number of words, characters, and punctuation in a text, and we combined numerical features into new variables. To create these features, we worked with transform primitives.

Featuretools also supports aggregation primitives. These primitives take related observations as input and return a single value. For example, if we have a numerical variable, price, related to an invoice, an aggregation primitive would take all the price observations for a single invoice and return a single value, such as the mean price or the sum (that is, the total amount paid), for that particular invoice.

Tip

The Featuretools aggregation functionality is the equivalent of groupby in pandas, followed by pandas functions such as mean, sum, std, and...