Replacing missing values with a value at the end of the variable distribution is equivalent to replacing them with an arbitrary value, but instead of identifying the arbitrary values manually, these values are automatically selected as those at the very end of the variable distribution. The values that are used to replace missing information are estimated using the mean plus or minus three times the standard deviation if the variable is normally distributed, or the inter-quartile range (IQR) proximity rule otherwise. According to the IQR proximity rule, missing values will be replaced with the 75th quantile + (IQR * 1.5) at the right tail or by the 25th quantile - (IQR * 1.5) at the left tail. The IQR is given by the 75th quantile - the 25th quantile.
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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