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)

Chapter 1 – Introduction to Data Imbalance in 
Machine Learning

  1. The choice of loss function when training a model can greatly affect the performance of the model on imbalanced datasets. Some loss functions may be more sensitive to class imbalance than others. For instance, a model trained with a loss function such as cross-entropy might be heavily influenced by the majority class and perform poorly on the minority class.
  2. The PR curve is more informative than the ROC curve when dealing with highly skewed datasets because it focuses on the performance of the classifier on the positive (minority) class, which is often the class of interest in imbalanced datasets. The ROC curve, on the other hand, considers both the TPR and the FPR and thus might give an overly optimistic view of the model’s performance when the negative class dominates the dataset.
  3. Accuracy can be a misleading metric for model performance on imbalanced datasets because it does not take...