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)

Minority class incremental rectification

Minority class incremental rectification is a deep learning technique that boosts the representation of minority classes in imbalanced datasets using a Class Rectification Loss (CRL). This strategy dynamically adjusts to class imbalance, enhancing model performance by incorporating hard example mining and other methods.

This technique is based on the paper by Dong et al. [5][6]. Here are the main steps of the technique:

  1. Class identification in each batch:
    • Binary classification: We consider a class as a minority if it makes up less than 50% of the batch. The rest is the majority class.
    • Multi-class classification: We define all minority classes as those that collectively account for no more than 50% of the batch. The remaining classes are treated as majority classes.
  2. Compute the class rectification loss:
    • Locate challenging samples:
      • Find hard positives: We identify samples from the minority class that our model incorrectly assesses with...