Book Image

Mastering Machine Learning Algorithms - Second Edition

By : Giuseppe Bonaccorso
Book Image

Mastering Machine Learning Algorithms - Second Edition

By: Giuseppe Bonaccorso

Overview of this book

Mastering Machine Learning Algorithms, Second Edition helps you harness the real power of machine learning algorithms in order to implement smarter ways of meeting today's overwhelming data needs. This newly updated and revised guide will help you master algorithms used widely in semi-supervised learning, reinforcement learning, supervised learning, and unsupervised learning domains. You will use all the modern libraries from the Python ecosystem – including NumPy and Keras – to extract features from varied complexities of data. Ranging from Bayesian models to the Markov chain Monte Carlo algorithm to Hidden Markov models, this machine learning book teaches you how to extract features from your dataset, perform complex dimensionality reduction, and train supervised and semi-supervised models by making use of Python-based libraries such as scikit-learn. You will also discover practical applications for complex techniques such as maximum likelihood estimation, Hebbian learning, and ensemble learning, and how to use TensorFlow 2.x to train effective deep neural networks. By the end of this book, you will be ready to implement and solve end-to-end machine learning problems and use case scenarios.
Table of Contents (28 chapters)
26
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Index

Introduction to Markov random fields

Let's consider a set of random variables, (normally drawn from the same distribution family despite there being no restrictions about the distributions that demand this must be so), organized in an undirected graph, G = {V, E}, as shown in the following diagram:

Example of a probabilistic undirected graph

Before analyzing the properties of the graph, we need to remember that two random variables, a and b, are conditionally independent given the random variable, c, if:

p(a, b|c) = p(a|c)p(b|c)

If all generic couples of subsets of variables are conditionally independent given a separating subset Sk (so that all connections between variables belonging to Si to variables belonging to Sj pass through Sk), the graph is called a Markov random field (MRF).

Given G = {V, E}, a subset containing vertices such that every couple is adjacent is called a clique (the set of all cliques is often denoted as cl(G)). For example, consider...