Julia 1.0 Programming Cookbook

How it works...

CategoricalArray is a type that can store nominal (unordered) or ordinal (ordered) categories.

A categorical array is typically created using the categorical function, which optionally allows a keyword argument, ordered, to specify whether it is nominal (ordered=false; the default) or ordinal (ordered=true).

Each categorical array has two important properties:

• If it is ordered, it can be checked using the isordered function
• A list of its levels, which can be checked using the levels function

A categorical array can be constructed from an array of any type, but strings have special treatment. They are always stored as String internally and such categorical values can be worked with as if they were normal strings. For example, ...