Lists, why would you need them?

Congratulations! At this point in the course you are already familiar with:

• Vectors (one dimensional array): can hold numeric, character or logical values. The elements in a vector all have the same data type.
• Matrices (two dimensional array): can hold numeric, character or logical values. The elements in a matrix all have the same data type.
• Data frames (two-dimensional objects): can hold numeric, character or logical values. Within a column all elements have the same data type, but different columns can be of different data type.

Pretty sweet for an R newbie, right? ;-)