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)

Preparing the data

In this chapter, we are going to use the classic MNIST dataset. This dataset contains 28-pixel x 28-pixel images of handwritten digits. The task for the model is to take an image as input and identify the digit in the image. We will use PyTorch, a popular deep-learning library, to demonstrate the algorithms. Let’s prepare the data now.

The first step in the process will be to import the libraries. We will need NumPy (as we deal with numpy arrays), torchvision (to load MNIST data), torch, random, and copy libraries.

Next, we can download the MNIST data from torchvision.datasets. The torchvision library is a part of the PyTorch framework, which contains datasets, models, and common image transformers for computer vision tasks. The following code will download the MNIST dataset from this library:

img_transform = torchvision.transforms.ToTensor()
trainset = torchvision.datasets.MNIST(\
    root='/tmp/mnist', train=True,\...