MATLAB Programming Fundamentals - MathWorks

Validate Number of Function Arguments

This example shows how to check whether your custom function receives a valid number

of input or output arguments. MATLAB performs some argument checks automatically.

For other cases, you can use narginchk or nargoutchk.

Automatic Argument Checks

MATLAB checks whether your function receives more arguments than expected when it

can determine the number from the function definition. For example, this function accepts

up to two outputs and three inputs:

function [x,y] = myFunction(a,b,c)

If you pass too many inputs to myFunction, MATLAB issues an error. You do not need to

call narginchk to check for this case.

[X,Y] = myFunction(1,2,3,4)

Error using myFunction

Too many input arguments.

Use the narginchk and nargoutchk functions to verify that your function receives:

• A minimum number of required arguments.


• No more than a maximum number of arguments, when your function uses varargin
  or varargout.

Input Checks with narginchk

Define a function in a file named testValues.m that requires at least two inputs. The

first input is a threshold value to compare against the other inputs.

function testValues(threshold,varargin)

minInputs = 2;

maxInputs = Inf;

narginchk(minInputs,maxInputs)

for k = 1:(nargin-1)

if (varargin{k} > threshold)

fprintf('Test value %d exceeds %d\n',k,threshold);

end

end

21 Function Arguments