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

Determining the number of principal components using the scree test


As we only need to retain the principal components that account for most of the variance of the original features, we can either use the Kaiser method, scree test, or the percentage of variation explained as the selection criteria. The main purpose of a scree test is to graph the component analysis results as a scree plot and find where the obvious change in the slope (elbow) occurs. In this recipe, we will demonstrate how to determine the number of principal components using a scree plot.

Getting ready

Ensure that you have completed the previous recipe by generating a principal component object and save it in the variable, swiss.pca.

How to do it...

Perform the following steps to determine the number of principal components with the scree plot:

  1. First, you can generate a bar plot by using screeplot:
        > screeplot(swiss.pca, type="barplot")  

The scree plot in bar plot form

  1. You can also generate a line plot by using screeplot...