How to Download and Install R The R software can be downloaded from: Click on download R link.

Transcription

1 Tutorial 1: Getting Acquainted with R (Windows version) How to Download and Install R The R software can be downloaded from: Click on download R link. Choose a CRAN mirror from a location closest to where you are. You will have to scroll down a ways to get to United States locations. 1

2 Click the appropriate link for the operating system you are using. The program requires Windows XP or later. Click the base link. Windows users should install and run the 64-bit version. Choose default settings for installing the program. Then click on Download R for Windows (or whatever the current version is). 2

3 Choose where to save the download or check your Downloads folder to find the files. Double-click the installation file and follow the instructions on your screen to install the program. Use default installation settings. Check back every few months for the latest version of the software. R Console Now open the program. There should be an icon installed on your desktop. The window you see is the R Console. This window will show you what code you have run and the output from that code. While you can type and run your code directly in this window, it is not recommended. Script Editor The best way to write, run, and save your code is by using the Script Editor. Create a new script in Script Editor by choosing File > New Script in the menu bar. 3

4 Saving a.r Script File The script editor creates.r document files that behave similar to Notepad. It allows you to write and edit your R code much easier than can be done in the R Console window. It also allows you to save your code (also called an R script ). To save your script, make sure you have the script editor window active, then go to File > Save As in the menu bar. Opening a Saved.R Script File Double-clicking on a.r script file will open both the R program and the.r file. Alternatively, you can first open the R program, then go to File > Open Script. In the window that pops up, browse to your.r script file and open it. Help Topics Help topics can be accessed by clicking Help in the menu bar. Search help... will open a small window for you to enter your search term(s). R functions (text) opens a help search window to search for specific commands. Html help will open a web browser for the R search engine. 4

5 Type in your search terms and click okay. The result is a list of help pages that match your search in some capacity. 5

6 Typing the name of a specific command into the parentheses of help() will open the help topics directly to that command. Running R Code There are a variety of options for running a line of R code (commands). To run a single line of code, place the cursor on the line of code you want to run. Multiple lines of code can be run at once by first highlighting all the lines you wish to run. To run the desired code, hold the Ctrl key and press the R key. You can also go to the menu bar: Edit > Run line or selection or Run all You can also right-click on the line of code and choose Run line or selection 6

7 Installing Packages Some commands require a package not already installed with the base R package. To download a package, go to Packages > Install package(s)... A new window will appear with a list of CRAN mirrors. Select the one closest to you. 7

8 A list of packages will appear. Multiple packages may be selected by holding crtl as you click. Once you ve selected the packages you want, click okay. Note: The default location for package installation is At System Level (in R framework) which is fine for beginners. Loading Packages To load a package that you have installed, use the library command, placing the name of the package in the parentheses. Packages must be reloaded every time you start a new R session. library(vegan) 8

9 Leave the parentheses blank to see which packages you have already installed in R. library() What s a File Pathname? How do I find it? In order to import your own data for use with the program, you need to know the file pathname, or where the file is stored. The file pathname is like an address for a file on your computer and is fairly easy to find. Go to the file and right-click on it. In the menu that pops up, choose Properties. In the window that appears, look for the location of the file. 9

10 Setting a Working Directory (Recommended) The best way to streamline your work, in order to easily read and write data files, is to set up a working directory where all data files associated with a project will be stored. This can be a dedicated folder somewhere on your computer. The other benefit to establishing a working directory is that it is the easiest way to save your outputs as new.csv files. The working directory folder should be kept in the same location, but if it must be moved, you can always change the pathname in the code that established the working directory for your R session. In the examples below, working directory folder is the name of the folder where your data files are stored. In Windows, the pathname for the working directory folder can be formatted two ways: setwd( C:/Documents and Settings/Owner/Desktop/working directory folder/ ) setwd( C:\\Documents and Settings\\Owner\\Desktop\\working directory folder\\ ) If you copy and paste the location from the Properties window, make sure you change the backslashes \ to forward slashes / or double backslashes \\. Note that the working directory pathname ends with the folder that contains the data files you want to work with. In Tutorial 2, we will see how to import datasets into R using the read.csv() and load() commands. Making Comments or Notes in R In your R script it can be helpful to label bits of code to help you remember what it does later. On a given line, anything that follows a pound symbol (#) will not be read by the program. mean(height) #calculates the mean of height data Closing the Program Save the Workspace Image? Beginner R users do not need to save the workspace image select no. In case you re curious, a workspace image saves everything done in an R session and automatically reloads it next time the program is opened. Advanced R users working on large projects find this useful, but for our purposes in this class, we do not need to worry about doing this. 10

11 Tutorial Code #the pound (hashtag) symbol can be used to make a note in your R script; anything that follows will not be read by the program #start the help topics server help() #search for the help topic on t.test help(t.test) #search for the help topic on mean help(mean) #see what packages you have installed library() #load a particular package that has been installed library(vegan) #set the working directory on a PC; you must change the file pathname for your own working directory location setwd( C:/Documents and Settings/JohnDoe/Desktop/R Class/ ) setwd( C:\\Documents and Settings\\JohnDoe\\Desktop\\R Class\\ ) 11