MATLAB Programming Fundamentals - MathWorks

Create Categorical Arrays

This example shows how to create a categorical array. categorical is a data type for

storing data with values from a finite set of discrete categories. These categories can

have a natural order, but it is not required. A categorical array provides efficient storage

and convenient manipulation of data, while also maintaining meaningful names for the

values. Categorical arrays are often used in a table to define groups of rows.

By default, categorical arrays contain categories that have no mathematical ordering. For

example, the discrete set of pet categories {'dog' 'cat' 'bird'} has no meaningful

mathematical ordering, so MATLAB® uses the alphabetical ordering {'bird' 'cat'

'dog'}. Ordinal categorical arrays contain categories that have a meaningful

mathematical ordering. For example, the discrete set of size categories {'small',

'medium', 'large'} has the mathematical ordering small < medium < large.

When you create categorical arrays from cell arrays of character vectors or string arrays,

leading and trailing spaces are removed. For example, if you specify the text {' cat' 'dog '}

as categories, then when you convert them to categories they become {'cat' 'dog'}.

Create Categorical Array from Cell Array of Character Vectors

You can use the categorical function to create a categorical array from a numeric

array, logical array, string array, cell array of character vectors, or an existing categorical

array.

Create a 1-by-11 cell array of character vectors containing state names from New

England.

state = {'MA','ME','CT','VT','ME','NH','VT','MA','NH','CT','RI'};

Convert the cell array, state, to a categorical array that has no mathematical order.

state = categorical(state)

state = 1x11 categorical array

Columns 1 through 9

MA ME CT VT ME NH VT MA NH

Columns 10 through 11

CT RI

8 Categorical Arrays