Many machine learning algorithms are sensitive to the scale and magnitude of the features. In particular, the coefficients of the linear models depend on the scale of the feature, that is, changing the feature scale will change the coefficients' value. In linear models, as well as 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. Thus, having features within a similar scale allows us to compare feature importance, and also helps algorithms converge faster, thus improving performance and training times. We discussed the effect of feature magnitude on algorithm performance in more detail in the Comparing feature magnitude recipe of Chapter 1, Foreseeing Variable Problems when Building ML Models. In this chapter...
Python Feature Engineering Cookbook
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Python Feature Engineering Cookbook
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Overview of this book
Feature engineering is invaluable for developing and enriching your machine learning models. In this cookbook, you will work with the best tools to streamline your feature engineering pipelines and techniques and simplify and improve the quality of your code.
Using Python libraries such as pandas, scikit-learn, Featuretools, and Feature-engine, you’ll learn how to work with both continuous and discrete datasets and be able to transform features from unstructured datasets. You will develop the skills necessary to select the best features as well as the most suitable extraction techniques. This book will cover Python recipes that will help you automate feature engineering to simplify complex processes. You’ll also get to grips with different feature engineering strategies, such as the box-cox transform, power transform, and log transform across machine learning, reinforcement learning, and natural language processing (NLP) domains.
By the end of this book, you’ll have discovered tips and practical solutions to all of your feature engineering problems.
Table of Contents (13 chapters)
Preface
Foreseeing Variable Problems When Building ML Models
Free Chapter
Imputing Missing Data
Encoding Categorical Variables
Transforming Numerical Variables
Performing Variable Discretization
Working with Outliers
Deriving Features from Dates and Time Variables
Performing Feature Scaling
Applying Mathematical Computations to Features
Creating Features with Transactional and Time Series Data
Extracting Features from Text Variables
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