This R data.table ultimate cheat sheet is different from many others because it’s interactive. You can search for a specific phrase like add column or by a type of task group such as Subset or ...

See how to join two data sets by one or more common columns using base R’s merge function, dplyr join functions, and the speedy data.table package.

For example, data_frame['I. quarter'][0] contains the value of the first cell of column I. quarter. In the Demo.xlsx worksheet, this is the turnover of district A in the first quarter (cell B2).