Hands-On Programming with R

Appendix D. Loading and Saving Data in R

This appendix will show you how to load and save data into R from plain-text files, R files, and Excel spreadsheets. It will also show you the R packages that you can use to load data from databases and other common programs, like SAS and MATLAB.

Data Sets in Base R

R comes with many data sets preloaded in the datasets package, which comes with base R. These data sets are not very interesting, but they give you a chance to test code or make a point without having to load a data set from outside R. You can see a list of R’s data sets as well as a short description of each by running:

help(package = "datasets")

To use a data set, just type its name. Each data set is already presaved as an R object. For example:

iris
##   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1          5.1         3.5          1.4         0.2  setosa
## 2          4.9         3.0          1.4         0.2  setosa
## 3          4.7         3.2          1.3         0.2  setosa
## 4          4.6         3.1          1.5         0.2  setosa
## 5          5.0         3.6          1.4         0.2  setosa
## 6          5.4         3.9          1.7         0.4  setosa

However, R’s data sets are no substitute for your own data, which you can load into R from a wide variety of file formats. But before you load any data files into R, you’ll need to determine where your working directory is.

Working Directory

Each time you open R, it links itself to a directory on your computer, which R calls the working directory. This is where R will look for files when you attempt to load them, and it is where R will save files when you save them. The location of your working directory ...