How can I check whether an argument is given or not (inputParser)?

205 Ansichten (letzte 30 Tage)
Ezor am 14 Dez. 2016
Kommentiert: Maikel Zhilin am 26 Dez. 2022
Hi everyone,
I think the title is pretty obvious ! To be a little bit more precise, I'm using an InputParser to let the user choose what arguments (s)he wants to use. Therefore I would like to check what optional inputs have been enter or not. InputParser allows to enter name,value paire for each variable and I need something to check if a specific argument exists among all of those enter when the function is called.
It appears that 'isempty' doesn't work. I've also try this but it failed too
if varargin{:,1} == 'arg_name'
disp('not ok')
(even if cell_structure(:,1)=='string' works outside a function)
Thanks in advance, Edward

Antworten (4)

Sean de Wolski
Sean de Wolski am 14 Dez. 2016
Bearbeitet: Sean de Wolski am 14 Dez. 2016
There's a 'UsingDefaults' property of the inputParser that is populated after it is parsed. This will tell you which variables are not using the default value.
  1 Kommentar
Ezor am 14 Dez. 2016
I had not thought about that but I seems to be a good solution to bypass this issue. Thank you

Melden Sie sich an, um zu kommentieren.

Guillaume am 14 Dez. 2016
Well, if the behaviour of your code is going to change depending on whether or not an optional input was given, then it's not really an optional input anymore.
inputParser does not offer the option of knowing which of the optional inputs were actually given. If you really need that, you're going to have to write your own input parser or reparse the optional parameters yourself.
  3 Kommentare
Ezor am 14 Dez. 2016
Thank you. That could do the trick. I'll try this and let you know if the ismember function suits my need.

Melden Sie sich an, um zu kommentieren.

Ian am 5 Dez. 2018
A bit late to the game here, but expanding on Sean de Wolski's brief suggestion, here is a code snippet that should satisfy. This is essentially the inverse of Guillaume's approach -- test for the absence of a parameter in the UsingDefaults
function test_used(varargin)
p = inputParser;
if (~ismember('opt1',p.UsingDefaults)), fprintf('opt1 present\n'); end
if (~ismember('arg1',p.UsingDefaults)), fprintf('arg1 present\n'); end
if (~ismember('arg2',p.UsingDefaults)), fprintf('arg2 present\n'); end
and showing results:
>> test_used(10)
opt1 present
>> test_used(10,'arg2','goodbye')
opt1 present
arg2 present
>> test_used('arg1','hello')
arg1 present
This is similar to Guillaume's solution above, which is also good, but won't work if you have optional positional parameters (addOptional(...) ) or if the parser's StructExpand it set to true.
For those curious why this is needed, or at least useful: it allows setting related parameters when an optional or key/value pair is specified, without overriding a user setting. For example, I might want to set arg2 to arg1's value if the user specifies arg1 only, but keep the user's arg2 setting if both arg1 and arg2 are passed in.
  1 Kommentar
Maikel Zhilin
Maikel Zhilin am 26 Dez. 2022
This < > helped me, thank you :)
< ~ismember('arg1',p.UsingDefaults) >

Melden Sie sich an, um zu kommentieren.

KSSV am 14 Dez. 2016
function Hello(varargin)
if nargin==1
disp('not okay')
It takes any inputs, for one input it says ok for other inputs it says not ok.
  4 Kommentare
KSSV am 15 Dez. 2016
function Hello(varargin)
N = nargin ;
inputs = cell(N,1) ;
for i = 1:N
inputs{i} = varargin{i} ;
Call it by Hello('Distance',3,'Velocity',{5})
Function will tell the classes of the inputs. Depending on your usage, you can code in the way you want.

Melden Sie sich an, um zu kommentieren.


Mehr zu Matrix Indexing finden Sie in Help Center und File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by