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

Principal components analysis (PCA)


The principal components analysis transforms an original set of features into a new set of features ordered by decreasing value of their variance. PCA enables the data scientist to select the features that have the most impact on the classification or prediction (features with the higher variance).

The original observations (vectors of feature instance) are transformed into a set of variables with a lower degree of correlation.

Let's consider a model with two features {x, y} and a set of observations {xi, yi} plotted in the following chart:

Visualization of the principal components for a two-dimensional model

The features x and y are converted into two variables, X and Y (that is rotation), to appropriately match the distribution of observations. The variable with the highest variance is known as the first principal component. In the generic case of multiple features, the variable with the n th highest variance is known as the n th principal component. The...