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      Andrie de Vries, Joris Meys

      R For Dummies

      R For Dummies®, 2nd Edition

      Published by: John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, www.wiley.com

      Copyright © 2015 by John Wiley & Sons, Inc., Hoboken, New Jersey

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      Published simultaneously in Canada

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      Library of Congress Control Number: 2015941928

      ISBN 978-1-119-05580-8 (pbk); ISBN 978-1-119-05583-9 (epub); 978-1-119-05585-3 (epdf)

      Introduction

      Welcome to R For Dummies, the book that helps you learn the statistical programming language R quickly and easily.

      We can’t guarantee that you’ll be a guru if you read this book, but you should be able to

      ✔ Perform data analysis by using a variety of powerful tools.

      ✔ Use the power of R to do statistical analysis and data-processing tasks.

      ✔ Appreciate the beauty of using vector-based operations (rather than loops) to do speedy calculations.

      ✔ Appreciate the meaning of the following line of code:

      knowledge <– apply(theory, 1, sum)

      ✔ Know how to find, download, and use code that has been contributed to R by its very active community of developers.

      ✔ Know where to find extra help and resources to take your R coding skills to the next level.

      ✔ Create beautiful graphs and visualizations of your data.

      About This Book

      R For Dummies is an introduction to the statistical programming language known as R. We start by introducing the interface and work our way from the very basic concepts of the language through more sophisticated data manipulation and analysis.

      We illustrate every step with easy-to-follow examples. This book contains numerous code snippets, several write-it-yourself functions you can use later on, and complete analysis scripts. All these are for you to try out yourself.

      We don’t attempt to give a technical description of how R is programmed internally, but we do focus as much on the why as on the how. R has many features that may seem surprising at first, so we believe it’s important to explain both how you should talk to R, and how the R engine interprets what you say. After reading this book, you should be able to manipulate your data in the form you want and understand how to use functions we didn’t cover in the book (as well as the ones we do cover).

      This book is a reference. You don’t have to read it from beginning to end. Instead, you can use the table of contents and index to find the information you need. We cross-reference other chapters where you can find more information.

      Changes in the Second Edition

      Since the publication of the first edition, R has kept evolving and improving. To keep the book accurate, we updated the code to reflect any changes in the latest version of R (version 3.2.0). With the feedback from readers, students, and colleagues we could rework some sections to clarify issues and correct inaccuracies. For example, we modified the code to use double quotes instead of single quotes when using text strings. We also refer to the fundamental units of lists as components, rather than elements.

      The new rfordummies package contains code examples in the book. Read all about it in Appendix B.

      R and RStudio

      R For Dummies can be used with any operating system that R runs on. Whether you use Mac, Linux, or Windows, this book will get you on your way with R.

      R is more a programming language than an application. When you download R, you automatically download a console application that’s suitable for your operating system. However, this application has only basic functionality, and it differs to some extent from one operating system to the next.

      RStudio is a cross-platform application, also known as an Integrated Development Environment (IDE) with some very neat features to support R. In this book, we don’t assume you use any specific console application. However, RStudio provides a common user interface across the major operating systems. For this reason, we use RStudio to demonstrate some of the concepts rather than any specific operating-system version of R.

      Conventions Used in This Book

      Code snippets appear like this example, where we simulate 1 million throws of two six-sided dice:

      > set.seed(42)

      > throws <– 1e6

      > dice <– replicate(2,

      +                   sample(1:6, throws, replace = TRUE)

      + )

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