How to Create Function in MATLAB: Syntax and Example

In MATLAB, you create a function by starting with the function keyword followed by the output variables, the function name, and input variables in parentheses. The function code goes below this line, and the file must be saved with the same name as the function.

Syntax

The basic syntax to create a function in MATLAB is:

• function: keyword to define a function
• [outputs]: output variables in square brackets (use no brackets if only one output)
• = functionName(inputs): function name and input variables in parentheses
• The function code follows below this line

The function file must be saved with the same name as functionName and with a .m extension.

matlab

function [output1, output2] = functionName(input1, input2)
    % Function code here
end

Example

This example shows a function named addAndMultiply that takes two inputs and returns their sum and product.

matlab

function [sumResult, productResult] = addAndMultiply(a, b)
    sumResult = a + b;
    productResult = a * b;
end

Output

[sumResult, productResult] = addAndMultiply(3, 4)

sumResult =
     7

productResult =
    12

Common Pitfalls

Common mistakes when creating functions in MATLAB include:

• Not saving the function file with the same name as the function.
• Forgetting the end keyword (optional in simple functions but recommended).
• Mismatching the number of output variables when calling the function.
• Using variables inside the function without defining them as inputs or outputs.

matlab

%% Wrong: File name and function name mismatch
function y = wrongName(x)
    y = x^2;
end

%% Right: File name and function name match
function y = squareNumber(x)
    y = x^2;
end

Quick Reference

Remember these tips when creating MATLAB functions:

• Function file name = function name + .m
• Use function keyword to start
• List outputs in square brackets if more than one
• List inputs in parentheses
• End function with end (recommended)

Key Takeaways

Start a MATLAB function with the function keyword followed by outputs, name, and inputs.

Save the function in a file named exactly as the function with a .m extension.

Use square brackets for multiple outputs and parentheses for inputs.

Always check that the function name and file name match to avoid errors.

Include the end keyword to clearly mark the function's end.