Create Functions in Files
Both scripts and functions allow you to reuse sequences of
commands by storing them in program files. Scripts are the simplest type of program,
since they store commands exactly as you would type them at the command line.
Functions provide more flexibility, primarily because you can pass input values and
return output values. For example, this function named
computes the factorial of a number (
n) and returns the result
function f = fact(n) f = prod(1:n); end
This type of function must be defined within a file, not at the command line. Often,
you store a function in its own file. In that case, the best practice is to use the same
name for the function and the file (in this example,
MATLAB® associates the program with the file name. Save the file either in the
current folder or in a folder on the MATLAB search path.
You can call the function from the command line, using the same syntax rules that apply to functions installed with MATLAB. For instances, calculate the factorial of 5.
x = 5; y = fact(5)
y = 120
Starting in R2016b, another option for storing functions is to include them at the end
of a script file. For instance, create a file named
mystats.m with a
few commands and two functions,
script calculates the permutation of
x = 3; y = 2; z = perm(x,y) function p = perm(n,r) p = fact(n)/fact(n-r); end function f = fact(n) f = prod(1:n); end
Call the script from the command line.
z = 6
Syntax for Function Definition
The first line of every function is the definition statement, which includes the following elements.
Use lowercase characters for the keyword.
Output arguments (optional)
If your function returns one output, you can specify the
output name after the
function myOutput = myFunction(x)
If your function returns more than one output, enclose the output names in square brackets.
function [one,two,three] = myFunction(x)
If there is no output, you can omit it.
Or you can use empty square brackets.
function  = myFunction(x)
Function name (required)
Valid function names follow the same rules as variable names. They must start with a letter, and can contain letters, digits, or underscores.
To avoid confusion, use the same name for both the function file and the first function within the file. MATLAB associates your program with the file name, not the function name. Script files cannot have the same name as a function in the file.
Input arguments (optional)
If your function accepts any inputs, enclose their names in parentheses after the function name. Separate inputs with commas.
function y = myFunction(one,two,three)
If there are no inputs, you can omit the parentheses.
When you define a function with multiple input or output arguments, list any required arguments first. This ordering allows you to call your function without specifying optional arguments.
Contents of Functions and Files
The body of a function can include valid MATLAB expressions, control flow statements, comments, blank lines, and nested functions. Any variables that you create within a function are stored within a workspace specific to that function, which is separate from the base workspace.
Program files can contain multiple functions. If the file contains only function definitions, the first function is the main function, and is the function that MATLAB associates with the file name. Functions that follow the main function or script code are called local functions. Local functions are only available within the file.
Functions end with either an
end statement, the end of the
file, or the definition line for a local function, whichever comes first. The
end statement is required if:
Any function in the file contains a nested function (a function completely contained within its parent).
The function is a local function within a function file, and any local function in the file uses the
The function is a local function within a script file.
Although it is sometimes optional, use
better code readability.