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
Call testValues with too few inputs.
testValues(10)
Error using testValues (line 4)
Not enough input arguments.
Call testValues with enough inputs.
testValues(10,1,11,111)
Test value 2 exceeds 10
Test value 3 exceeds 10
21 Function Arguments
21-6