A lot of data comes in the form of flat files: simple tabular text files. Learn how to import the common formats of flat file data with base R functions.
In addition to base R, there are dedicated packages to easily and efficiently import flat file data. We'll talk about two such packages: readr and data.table.
Excel is a widely used data analysis tool. If you prefer to do your analyses in R, though, you'll need an understanding of how to import .csv data into R. This chapter will show you how to use readxl and gdata to do so.
Beyond importing data from Excel, you can take things one step further with XLConnect. Learn all about it and bridge the gap between R and Excel.