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

Nelson-Aalen Estimator of cumulative hazard


We have seen the Cox proportional hazard estimator in the previous recipe The Nelson-Aalen estimator is a non-parametric estimator that estimates the cumulative number of expected events. It gives an idea about the hazard rate shape.

Getting ready

You need to have performed the recipe dealing with the Cox proportional hazard.

How to do it...

Perform the following steps in R:

> sfitall = survfit(Surv(time, status)~1, data =cancer)
> c = coxph(formula=Surv(time, status)~1, data=cancer)
> n=basehaz(c)

Printing n will display all the hazard values with time. Plotting the same will be easy to understand:

> plot(n)

Plot of hazard and time

How it works...

Using the basehaz function will compute the hazard estimator for the Cox model using the Breslow estimator, which will be the same as the Nelson-Aalen estimator. It can also be computed using the cumsum function, which returns cumulative sums. The hazard function is simply an event divided by risk...