Book Image

Machine Learning Algorithms - Second Edition

Book Image

Machine Learning Algorithms - Second Edition

Overview of this book

Machine learning has gained tremendous popularity for its powerful and fast predictions with large datasets. However, the true forces behind its powerful output are the complex algorithms involving substantial statistical analysis that churn large datasets and generate substantial insight. This second edition of Machine Learning Algorithms walks you through prominent development outcomes that have taken place relating to machine learning algorithms, which constitute major contributions to the machine learning process and help you to strengthen and master statistical interpretation across the areas of supervised, semi-supervised, and reinforcement learning. Once the core concepts of an algorithm have been covered, you’ll explore real-world examples based on the most diffused libraries, such as scikit-learn, NLTK, TensorFlow, and Keras. You will discover new topics such as principal component analysis (PCA), independent component analysis (ICA), Bayesian regression, discriminant analysis, advanced clustering, and gaussian mixture. By the end of this book, you will have studied machine learning algorithms and be able to put them into production to make your machine learning applications more innovative.
Table of Contents (19 chapters)

Atom extraction and dictionary learning

Dictionary learning is a technique that allows you to rebuild a sample starting from a sparse dictionary of atoms (similar to principal components, but without constraints about the independence). Conventionally, when the dictionary contains a number of elements less than the dimensionality of the samples m, it is called under-complete, and on the other hand it's called over-complete when the number of atoms is larger (sometimes much larger) than m.

In Online Dictionary Learning for Sparse Coding, Mairal J., Bach F., Ponce J., Sapiro G., Proceedings of the 29th International Conference on Machine Learning, 2009, there's a description of the same online strategy adopted by scikit-learn, which can be summarized as a double optimization problem.

Let's suppose that we have a dataset, X:

Our goal is to find both a dictionary D...