R is all about data structures. Everything is built from vectors and lists. Arrays are vectors with a &#x27;dimension&#x27; attribute. Data-frames are lists of vectors of the same length. And so on. And factors, which again are a kind of vector, are the primary tool for partitioning the data in groups, so you can have &#x27;ragged&#x27; arrays. When you understand how all these work together you get the hang of R.