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

Compressing images with SVD


In the previous recipe, we demonstrated how to factorize a matrix with SVD and then reconstruct the dataset by multiplying the decomposed matrix. Furthermore, the application of matrix factorization can be applied to image compression. In this recipe, we will demonstrate how to perform SVD on the classic image processing material, Lenna.

Getting ready

In this recipe, you should download the image of Lenna beforehand (refer to http://www.ece.rice.edu/~wakin/images/lena512.bmp for this), or you can prepare an image of your own to see how image compression works.

How to do it...

Perform the following steps to compress an image with SVD:

  1. First, install and load bmp:
> install.packages("bmp")> library(bmp)
  1. You can then read the image of Lenna as a numeric matrix with the read.bmp function. When the reader downloads the image, the default name is lena512.bmp:
        > lenna = read.bmp("lena512.bmp")  
  1. Rotate and plot the image:
        > lenna = t(lenna)[,nrow(lenna...