Book Image

Machine Learning with R Cookbook, Second Edition - Second Edition

By : Yu-Wei, Chiu (David Chiu)
Book Image

Machine Learning with R Cookbook, Second Edition - Second Edition

By: Yu-Wei, Chiu (David Chiu)

Overview of this book

Big data has become a popular buzzword across many industries. An increasing number of people have been exposed to the term and are looking at how to leverage big data in their own businesses, to improve sales and profitability. However, collecting, aggregating, and visualizing data is just one part of the equation. Being able to extract useful information from data is another task, and a much more challenging one. Machine Learning with R Cookbook, Second Edition uses a practical approach to teach you how to perform machine learning with R. Each chapter is divided into several simple recipes. Through the step-by-step instructions provided in each recipe, you will be able to construct a predictive model by using a variety of machine learning packages. In this book, you will first learn to set up the R environment and use simple R commands to explore data. The next topic covers how to perform statistical analysis with machine learning analysis and assess created models, covered in detail later on in the book. You'll also learn how to integrate R and Hadoop to create a big data analysis platform. The detailed illustrations provide all the information required to start applying machine learning to individual projects. With Machine Learning with R Cookbook, machine learning has never been easier.
Table of Contents (21 chapters)
Title Page
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface

Using the COX proportional hazard model


The survival function gives the probability that a subject will survive up to time t where t moves to infinity. The hazard function is a rate at which an event occurs or the potential that an event will occur, per time unit. The survfit function works on the basis of the Kaplan-Meier method which works best when we have to represent two categories such as gender (male or female), as shown previously. It fails when the categories are increased.

In a Cox proportional hazards regression model, the measure of effect is the hazard rate, which is the risk of failure (the risk or probability of suffering the event of interest), given that the participant has survived up to a specific time. A probability must lie in the range 0 to 1. However, the hazard represents the expected number of events per one unit of time. As a result, the hazard in a group can exceed 1. For example, if the hazard is 0.2 at time t and the time units are months, then on average, 0.2...