Preparing Your Workplace for an Analysis

Create a working directory

Usually, people want to keep the folder structure on their computers tidy, so that they and their co-workers understand, which documents and data were used for a particular project – even if that project was finished months ago. This should also be the case when you work with R. Therefore, I recommend to create a new folder for every new project, which becomes the so-called working directory. There you put all the files, which are necessary for a project. For example, for this introduction I created the folder r_intro in my file explorer and I recommend to do the same on your computer now.

Obtain the original data

The data should be downloaded from the website and saved in the working directory now.

Create a new R script

You can either use the script you have already open from the 1+2 example above or click on the button with the plus sign on the top left of the editor window and then choose R Script to create a new script. Eventually, you should save that script in your working directory by clicking on the blue save button or on FileSave As…. It is recommended that the file has a telling name. For this intro the name my_first_r_experience will do. After clicking on Save the script saved in the .R format.

Set the working directory in R

Before we start our analysis, we should set the path to the working directory in R. The reason for this is a bit technical. Let’s suppose that we want to use R to access a certain file on our computer. There is no way, that R would automatically know in which folder this file is located, if we only specified its name. Therefore, we would not only have to provide the filename, but also the path to it. This can become cumbersome if we want to access many files with R. But given that we have put all the necessary data for our project in the folder r_intro, we only have to enter the path once by setting the working directory. Basically, it tells R to access this directory by default, whenever it has to use a file on the hard drive.1 The working directory of R can be set with the setwd function:

setwd("C:/path/to/your/working/directory/r_intro")

Recall that a function in R has a name and at least one argument. In the previous line setwd is the name of the function and the path to the working directory is the argument. Note that the path to the working directory has to be in quotation marks "path/to/your/working/directory" and the folders have to be separated by slashes / and not backslashes \ as they would be inserted when you directly copy a path from the Windows explorer into R.

Load the packages you need

Having installed all the necessary packages does not mean, that we can use them without any further action. Before we use the functions of a particular package, we have to load the package whenever R is started.2 This is commonly done with the library(packagename) function.3

library(foreign)

  1. However, you can also import data from different folders than your working directory, if you provide the full path to a file. This can be useful if you have a common data base, which should not be copied too often in order to save memory or to ensure that you always access the most recent data.

  2. Note that you have to install a package only once, whereas you have to load a package every time you start R.

  3. There is also a function called require which, basically, does the same as library. However, it also gives out the value TRUE if the package was loaded successfully and FALSE if not. This can be useful when you want your script to check, whether a certain package is installed on a machine. For example, if a co-worker uses the script and misses a certain package, require can be used to indicate this.