6  Lists

First, everyone should know how to use MS Excel to work with Sheets and do the following:

• Make formulas that reference many cells and multiple sheets.
  
• Use $

In R lists are very general data structures that can contain other data structures, such as, numbers, vectors, matricies, dataframes, and other lists. Being familiar with lists shows a level of maturity as an R user.

See the nycflights13:: datasets, they are all dataframes. See the dslabs::mnist_27 dataset, it is a list that contains a mixture of dataframes, lists and numbers.