MATLAB Programming Fundamentals - MathWorks

Input Parser Validation Functions

This topic shows ways to define validation functions that you pass to the Input Parser to

check custom function inputs.

The Input Parser methods addRequired, addOptional, and addParameter each

accept an optional handle to a validation function. Designate function handles with an at

(@) symbol.

Validation functions must accept a single input argument, and they must either return a

scalar logical value (true or false) or error. If the validation function returns false, the

Input Parser issues an error and your function stops processing.

There are several ways to define validation functions:

• Use an existing MATLAB function such as ischar or isnumeric. For example, check
  that a required input named num is numeric:

p = inputParser;

checknum = @isnumeric;

addRequired(p,'num',checknum)

parse(p,'text')

The value of 'num' is invalid. It must satisfy the function: isnumeric.

• Create an anonymous function. For example, check that input num is a numeric scalar
  greater than zero:

p = inputParser;

checknum = @(x) isnumeric(x) && isscalar(x) && (x > 0);

addRequired(p,'num',checknum)

parse(p,rand(3))

The value of 'num' is invalid. It must satisfy the function: @(x) isnumeric(x) && isscalar(x)

&& (x>0).

• Define your own function, typically a local function in the same file as your primary
  function. For example, in a file named usenum.m, define a local function named
  checknum that issues custom error messages when the input num to usenum is not a
  numeric scalar greater than zero:

function usenum(num)

p = inputParser;

Input Parser Validation Functions