R for Introductory Statistics Bret Larget September 25 2002 The aim of this document is to help you an undergraduate student in an introductory statistics course learn to use the software R as part of your learning of statistics If you find that it reads like the rough draft of something that could be more useful and better written that is because it is a rough draft that could be more useful and better written This document will evolve on a weekly basis as the semester progresses I will add new material as we cover it in class and edit old material based on feedback from you to make it clearer for you and future students I suggest that you do not print new versions but merely replace your electronic copy from time to time Good luck as you begin your quest to master introductory statistical concepts and their application 1 What is R R is powerful software for interacting with data With R you can create sophisticated graphs you can carryout statistical analyses and you can create and run simulations R is also a programming language with an extensive set of built in functions so you can with some experience extend the language and write your own code to build your own statistical tools Advanced users can even incorporate functions written in other languages such as C C and Fortran The S language has been around for more than twenty years and has been the most widely used statistical software in departments of statistics for most of that time first as S and then as the commercially available S PLUS R is an open source implementation of the S language that is now a viable alternative to S PLUS and in fact has many advantages A core team of statisticians and many other contributors work to update and improve R and to make versions that run well under all of the most popular operating systems Most importantly to you R is free high quality statistical software that will be useful as you learn statistics even though it is also a first rate tool for professional statisticians Why use R for introductory statistics There are several reasons that make R an excellent choice of statistical software for an introductory statistical course First R is free and available on the Web You can use it on your home computers and are not tied to campus labs Second R is powerful widely used software The knowledge of R you gain during the course potentially translates to a marketable skill You will learn to use a tool that has many practical uses outside the classroom Third even though it is not the simplest statistical software the basics are easy enough to master that learning to use R need not interfere overly much with learning the statistical concepts encountered in an introductory course Fourth did I mention that it is free and you can use it at home The primary drawback to using R in an introductory course is that most existing documentation for R 1 is written for an audience that is knowledgable about statistics and has experience with other statistical computing programs In contrast this document intends to make R accessible to the typical student in an introductory statistics course who is new to both statistical concepts and statistical computing The aim is to teach you how to install R on your home computer and to teach you to use R to learn the statistical concepts usually included in an introductory course with explanations and examples aimed at the appropriate level This document purposely does not attempt to teach you about R s advanced features The intention is to teach you enough R to enhance your learning of introductory statistics and to point you in the direction of more information should you find a desire to learn more 2 Installing R Installing R on your computer is simple if you have clear directions you can find that tell you exactly what to do in a way that is easy to understand Directions exist at the R website http cran r project org for installing R but many students may have difficulty determining which files they need to download and then how to install them Here are more explicit instructions that tell you what to do Obtaining the software There are two options for installing the software downloading it from the Web or installing from a prepared CD If you have a fast Internet connection a direct campus connection cable modem or DSL I recommend that you download the software If you have no Internet connection or are limited to a regular modem I recommend that you borrow a CD from me In either case there is only one file that you need to obtain different depending on the operating system Running this file begins the installation process which is straight forward Downloading R from the Web Go the R homepage at http cran us r project org Windows 95 or later Click on the link Windows 95 and later then click on the link base and finally click on SetupR exe which begins the download After the download is complete double click on the downloaded file and follow the on screen installation instructions Macintosh Click on the link MacOS System 8 6 to 9 1 and MacOS X then click on the link base and finally click on rm151 sit which begins the download After the download is complete double click on the downloaded file and follow the on screen installation instructions Loading R from a CD Insert the CD into the drive open the CD from My Computer in Windows and double click on the SetupR exe icon to begin installation Follow the on screen installation instructions 2 3 A First Session with R Starting and Quitting Because most students in the course are running R under Windows these instructions will assume that you are using the Windows version Apologies to the few Mac users I actually run R most often under Linux If you notice differences in what I write and how R actually performs under Windows please let me know Begin R by double clicking on the shortcut if you added a shortcut to your Desktop or from the Start button followed by the Program menu R will open with a command window with a prompt that awaits your first command R is a command line program You interact with the software by typing in commands which the program then interprets and acts on When you are done with your R session you can quit from the File menu or by typing q in the command window at the prompt Several Examples Here is a demonstration of several functions you will use frequently A later section will provide more details In these examples I will look at a data set from the textbook Statistics for the Life Sciences
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