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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27
Index

Random forests

A random forest is the bagging ensemble model based on decision trees. If the reader is not familiar with this kind of model, I suggest reading Alpaydin E., Introduction to Machine Learning, The MIT Press, 2010, where a complete explanation can be found. However, for our purposes, it's useful to provide a brief explanation of the most important concepts.

Random forest fundamentals

A decision tree is a model that resembles a standard hierarchical decision process. In the majority of cases, a special family is employed, called binary decision trees, as each decision yields only two outcomes. This kind of tree is often the simplest and most reasonable choice and the training process (which consists of building the tree itself) is very intuitive. The root contains the whole dataset:

Each level is obtained by applying a selection tuple, defined as follows:

The first index of the tuple corresponds to an input feature, while the threshold ti is a value...