Book Image

Machine Learning for Imbalanced Data

By : Kumar Abhishek, Dr. Mounir Abdelaziz
Book Image

Machine Learning for Imbalanced Data

By: Kumar Abhishek, Dr. Mounir Abdelaziz

Overview of this book

As machine learning practitioners, we often encounter imbalanced datasets in which one class has considerably fewer instances than the other. Many machine learning algorithms assume an equilibrium between majority and minority classes, leading to suboptimal performance on imbalanced data. This comprehensive guide helps you address this class imbalance to significantly improve model performance. Machine Learning for Imbalanced Data begins by introducing you to the challenges posed by imbalanced datasets and the importance of addressing these issues. It then guides you through techniques that enhance the performance of classical machine learning models when using imbalanced data, including various sampling and cost-sensitive learning methods. As you progress, you’ll delve into similar and more advanced techniques for deep learning models, employing PyTorch as the primary framework. Throughout the book, hands-on examples will provide working and reproducible code that’ll demonstrate the practical implementation of each technique. By the end of this book, you’ll be adept at identifying and addressing class imbalances and confidently applying various techniques, including sampling, cost-sensitive techniques, and threshold adjustment, while using traditional machine learning or deep learning models.
Table of Contents (15 chapters)

When to avoid undersampling the majority class

Undersampling is not a panacea and may not always work. It depends on the dataset and model under consideration:

  • Too little training data for all the classes: If the dataset is already small, undersampling the majority class can lead to a significant loss of information. In such cases, it is advisable to try gathering more data or exploring other techniques, such as oversampling the minority class to balance the class distribution.
  • Majority class equally important or more important than minority class: In specific scenarios, such as the spam filtering example mentioned in Chapter 1, Introduction to Data Imbalance in Machine Learning, it is crucial to maintain high accuracy in identifying the majority class instances. In such situations, undersampling the majority class might reduce the model’s ability to accurately classify majority class instances, leading to a higher false positive rate. Instead, alternative methods...