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 bag-of-words and n-grams

A Bag-of-Words (BoW) is a simplified representation of a piece of text that captures the words that are present in the text and the number of times each word appears in the text. So, for the text string Dogs like cats, but cats do not like dogs, the derived BoW is as follows:

dogs

like

cats

but

do

not

2

2

2

1

1

1

Figure 11.4 – BoW derived from the sentence “Dogs like cats, but cats do not like dogs”

Here, each word becomes a variable, and the value of the variable represents the number of times the word appears in the string. As you can see, BoW captures multiplicity but does...