Book Image

Scala for Machine Learning, Second Edition - Second Edition

Book Image

Scala for Machine Learning, Second Edition - Second Edition

Overview of this book

The discovery of information through data clustering and classification is becoming a key differentiator for competitive organizations. Machine learning applications are everywhere, from self-driving cars, engineering design, logistics, manufacturing, and trading strategies, to detection of genetic anomalies. The book is your one stop guide that introduces you to the functional capabilities of the Scala programming language that are critical to the creation of machine learning algorithms such as dependency injection and implicits. You start by learning data preprocessing and filtering techniques. Following this, you'll move on to unsupervised learning techniques such as clustering and dimension reduction, followed by probabilistic graphical models such as Naïve Bayes, hidden Markov models and Monte Carlo inference. Further, it covers the discriminative algorithms such as linear, logistic regression with regularization, kernelization, support vector machines, neural networks, and deep learning. You’ll move on to evolutionary computing, multibandit algorithms, and reinforcement learning. Finally, the book includes a comprehensive overview of parallel computing in Scala and Akka followed by a description of Apache Spark and its ML library. With updated codes based on the latest version of Scala and comprehensive examples, this book will ensure that you have more than just a solid fundamental knowledge in machine learning with Scala.
Table of Contents (27 chapters)
Scala for Machine Learning Second Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface
Index

Comparing CRF and HMM


A complete comparison of CRF and HMM models is beyond the scope of this book. However, there are some obvious differences due to the simple fact that HMM is a generative model and CRF is a discriminative model.

Contrary to the hidden Markov model, the conditional random field does not require the observations to be independent beside the time and order dependency. The conditional random field can be regarded as a generalization of the HMM: It extends the transition probabilities to arbitrary feature functions that can depend on the input sequence. You need to remember that HMM assumes the transition probabilities matrix to be constant.

HMM learns the transition probabilities, aij, on its own by training on an increasing amount of input data. The HMM is a special case of CRF where the probabilities used in the state transition are constant.