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)

Transforming variables with the logarithm function

The logarithm function is a powerful transformation for dealing with positive data with a right-skewed distribution (observations accumulate at lower values of the variable). A common example is variable income, with a heavy accumulation of values toward smaller salaries. The log transform has a strong effect on the shape of the variable distribution.

In this recipe, we will perform logarithmic transformation using NumPy, scikit-learn, and Feature-engine. We will also create a diagnostic plot function to evaluate the effect of the transformation on the variable distribution.

Getting ready

To evaluate the variable distribution and understand whether a transformation improves value spread and stabilizes the variance, we can visually inspect the data with histograms and Quantile-Quantile (Q-Q) plots. A Q-Q plot helps us determine whether two variables show a similar distribution. In a Q-Q plot, we plot the quantiles of one variable...