Understanding ans in MATLAB | Episode 1

In MATLAB, ans is a special variable that automatically stores the result of expressions or function calls that are not assigned to any variable. It's a handy feature for quickly checking results or performing calculations on the fly in the Command Window. However, its use comes with certain precautions in scripts or functions.

What is ans?

• Temporary Storage: ans acts as a placeholder for results of calculations or function outputs where no explicit variable is defined.

• Workspace-Specific: ans is specific to the workspace it's used in. MATLAB maintains separate instances of ans for the base workspace and each function workspace.

Why Caution is Advised

• Changeability: The value of ans can change with each operation that produces an output without an explicit assignment, making it unreliable for storing the results you wish to keep.

• Readability: Using ans in scripts or functions can make your code harder to read and understand, especially for others reviewing your work.

Examples and Best Practices

Example 1: Simple Calculation

% Performing a calculation without assigning the result to a variable.
2 + 2

% MATLAB stores the result in `ans`.

% Output: ans = 4

Example 2: Using ans for Further Calculations

% After the above operation, `ans` is 4.
% You can use `ans` in another calculation.

ans * 2

% Output: ans = 8

Note: While this demonstrates ans's utility, it's better practice to assign results to descriptive variables.

Example 3: Assigning Results to Variables

% A better approach: assigning the result to a variable.

result = 4 + 4

% Output: result = 8

After this operation, result holds the value 8, and ans remains unchanged from its last assignment unless another unassigned calculation or function call is made.

Example 4: Call a Function That Returns Output

function a = outputFunc()
    a = 100;
end

% call 'outputFunc' in MATLAB

Call 'outputFunc ' in MATLAB will store the returned result in the 'ans' if an output variable is not specified to save the result of a function.

outputFunc

after calling 'outputFunc' the 'ans' will have a value of 100.

% Performing a calculation without assigning the result to a variable.
2 + 2

MATLAB will store the above result in the ans and after calling 'outputFunc' with an output variable assignment:

saveResult = outputFunc

the 'saveResult' variable will have a value of 100 and ans will still be holding a value of 4.

Example 5: Using ans within the function

function result = useAnsExample()
    2 + 2; % This operation's result is not assigned to a variable
    result = ans * 10; % ans now holds the value 4 from the previous operation
end

Best Practices

1. Use Descriptive Variable Names: Instead of relying on ans for storing results, assign outputs to variables with meaningful names.

2. Limitans Usage to Interactive Exploration: ans is most useful for quick calculations in the Command Window, not in scripts or functions.

3. Maintain Readability: For clearer, more maintainable code, avoid using ans in your scripts or functions. Directly assign outputs to well-named variables.

Youtube Tutorial

Conclusion

While ans is a convenient feature in MATLAB for quick calculations and checks, understanding its behavior and limitations is crucial for effective and clear MATLAB programming. By following best practices and using ans judiciously, you can enhance the readability and reliability of your code.