MATLAB Programming Fundamentals - MathWorks

defined as character vectors, which can be costly to store and manipulate in a cell array

of character vectors or char array. Categorical arrays store only one copy of each

category name, often reducing the amount of memory required to store the array.

Create a sample cell array of character vectors.

state = [repmat({'MA'},25,1);repmat({'NY'},25,1);...

repmat({'CA'},50,1);...

repmat({'MA'},25,1);repmat({'NY'},25,1)];

Display information about the variable state.

whos state

Name Size Bytes Class Attributes

state 150x1 17400 cell

The variable state is a cell array of character vectors requiring 17,400 bytes of memory.

Convert state to a categorical array.

state = categorical(state);

Display the discrete categories in the variable state.

categories(state)

ans = 3x1 cell array

{'CA'}

{'MA'}

{'NY'}

state contains 150 elements, but only three distinct categories.

Display information about the variable state.

whos state

Name Size Bytes Class Attributes

state 150x1 500 categorical

There is a significant reduction in the memory required to store the variable.

8 Categorical Arrays