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Kobi
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how to create function without having to use all the inputs in the script

Asked by Kobi
on 24 Oct 2014
Latest activity Edited by Guillaume
on 24 Oct 2014
i have a function with many inputs how can i write this function so i would not have to fill all the inputs? for example now i have this function
T=Tavg('none',12,[],[])
to avoid using the last 2 inputs i must set them to empty array in the script

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2 Answers

Answer by Guillaume
on 24 Oct 2014
Edited by Guillaume
on 24 Oct 2014
 Accepted Answer

You have several options:
1. Use empty matrices as you have done. Advantages: Optional arguments can be anywhere. Disadvantages: You still have to pass empty matrices for optional arguments.
function T = Tavg(a,b,c,d)
if isempty(a)
a = defaulta;
end
%same for b,c,d
usage:
T = Tavg(a, [], c, []);
2. Use nargin as per James example. Advantages: dead simple. Disadvantages: Only the last(s) argument(s) is(are) optional. You can't have an optional argument in the middle
3. Use the property/value pair that mathworks use for a number of functions like plot. Advantages: Very flexible. Disadvantages: you have to do all the parsing and the user has to refer to the documentation to know the names of the properties.
function T = Tavg(varargin)
a = defaulta; b = defaultb; ...
for opt = 1:3:nargin
switch varargin{opt}
case 'a'
a = varargin{opt+1};
case 'b'
b = varargin{opt+1};
...
usage:
T = Tavg('a', a, 'c', c);
4. Use a class for your function and class property for the optional arguments (like a functor, if you're familiar with C++). Advantages: Very flexible. Automatic tab completion for arguments. Self-documented. Can be reused without having to reenter the arguments. Disadvantages: usage may be too unusual for some people as it's OOP.
classdef Tavg
properties
a = defaulta;
b = defaultb;
...
end
methods
function T = Apply(this)
T = this.a + this.b - this.c * this.d;
end
end
end
usage:
TAvgfun = Tavg;
TAvgfun.a = a;
Tavgfun.c = c;
T = Tavgfun.Apply(); % or T = Apply(TAvgfun);

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Answer by James Tursa
on 24 Oct 2014

Use nargin in your function to determine how many inputs are actually being passed in. E.g.
function T = Tavg(a,b,c,d)
if( nargin == 2 )
c = something; % c wasn't passed in
d = something; % d wasn't passed in
end
etc.

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