Book Image

Learning Bayesian Models with R

By : Hari Manassery Koduvely
Book Image

Learning Bayesian Models with R

By: Hari Manassery Koduvely

Overview of this book

Bayesian Inference provides a unified framework to deal with all sorts of uncertainties when learning patterns form data using machine learning models and use it for predicting future observations. However, learning and implementing Bayesian models is not easy for data science practitioners due to the level of mathematical treatment involved. Also, applying Bayesian methods to real-world problems requires high computational resources. With the recent advances in computation and several open sources packages available in R, Bayesian modeling has become more feasible to use for practical applications today. Therefore, it would be advantageous for all data scientists and engineers to understand Bayesian methods and apply them in their projects to achieve better results. Learning Bayesian Models with R starts by giving you a comprehensive coverage of the Bayesian Machine Learning models and the R packages that implement them. It begins with an introduction to the fundamentals of probability theory and R programming for those who are new to the subject. Then the book covers some of the important machine learning methods, both supervised and unsupervised learning, implemented using Bayesian Inference and R. Every chapter begins with a theoretical description of the method explained in a very simple manner. Then, relevant R packages are discussed and some illustrations using data sets from the UCI Machine Learning repository are given. Each chapter ends with some simple exercises for you to get hands-on experience of the concepts and R packages discussed in the chapter. The last chapters are devoted to the latest development in the field, specifically Deep Learning, which uses a class of Neural Network models that are currently at the frontier of Artificial Intelligence. The book concludes with the application of Bayesian methods on Big Data using the Hadoop and Spark frameworks.
Table of Contents (11 chapters)
10
Index

Performance metrics for classification


To understand the concepts easily, let's take the case of binary classification, where the task is to classify an input feature vector into one of the two states: -1 or 1. Assume that 1 is the positive class and -1 is the negative class. The predicted output contains only -1 or 1, but there can be two types of errors. Some of the -1 in the test set could be predicted as 1. This is called a false positive or type I error. Similarly, some of the 1 in the test set could be predicted as -1. This is called a false negative or type II error. These two types of errors can be represented in the case of binary classification as a confusion matrix as shown below.

Confusion Matrix

Predicted Class

Positive

Negative

Actual Class

Positive

TP

FN

Negative

FP

TN

From the confusion matrix, we can derive the following performance metrics:

  • Precision: This gives the percentage of correct answers in the output predicted as positive
  • Recall: This gives the percentage...