For some data.table users, “dot-SD” is a bit of a mystery. But data.table creator Matt Dowle told me that it’s actually quite simple: Just think of it as a symbol representing “each group ...

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.

Select cells E3:L16. Go to Data, click the dropdown arrow next to What-if Analysis within the Forecast group, and choose Data Table. The Data Table window will open, asking for inputs into Row input ...