Review of ND-Arrays

• Vectors and matrices are just special cases of a more general data structure: arrays (or sometimes, ND-arrays).

• Everything we learned about vectors and matrices can be generalized in a relatively straightforward manner to arrays with more than two dimensions (mostly just by including more entries between our square brackets when subsetting).

• We can often do mathematical operations with arrays of different shapes and even arrays with different numbers of dimensions. The way this works is governed by the rules of broadcasting.