Matlab function assumed inputs

Does Matlab support functions with inputs that if not given, can be assumed?

I would like to write some code similar to the following - where if alpha and beta are not given when calling the function they are assigned to a set value 10 and -0.1 respectively

function [x,y] = pricingprogramme(P,T,alpha = 10, beta = -0.1)

... some code using P,T aswell as alpha and beta ....

end

Any help would be greatly appreciated.

Answer 1

[Dyuman Joshi]

Yes, use varargin with nargin -

[x1,y1] = pricingprogramme(5,10)

x1 = 16

y1 = 40.1000

[x2,y2] = pricingprogramme(1,2,3,4)

x2 = -9

y2 = -5

function [x,y] = pricingprogramme(P,T, varargin)
if nargin == 4
    alpha = varargin{1};
    beta = varargin{2};
elseif nargin==2
    alpha = 10;
    beta = -0.1;
else
    %Modify other cases as per need
    error('Number of inputs must be 2 or 4')
end

%Random definitions
x = P + T - alpha*beta;
y = P*T - (alpha + beta);
end

[Benjamin Wilson]

Thank you! Very helpul!

Answer 2

[Stephen23]

The simplest approach is to use the ARGUMENTS block:

https://www.mathworks.com/help/matlab/ref/arguments.html

https://www.mathworks.com/help/matlab/matlab_prog/function-argument-validation-1.html

pricingprogramme([],[])

ans = 10.1000

pricingprogramme([],[],3,0.5)

ans = 3.5000

function out = pricingprogramme(P,T,alpha,beta)
arguments
    P
    T
    alpha = 10
    beta  = 0.1
end
out = alpha + beta;
end

Answer 3

[Florian Bidaud]

Hi,

if you want positional arguments, use addOptional with an inputParser like this :

% to use the function as 
% [x,y] = pricingprogramme(P, T, alpha_value, beta_value) 
% or pricingprogramme(P, T, alpha_value) 
% or pricingprogramme(P, T)
function [x,y] = pricingprogramme(P,T,varargin)
    p = inputParser;
    addOptional(p,'alpha',10, @isnumeric)
    addOptional(p,'beta',0.1, @isnumeric)
    parse(p,varargin{:})
    alpha = p.Results.alpha;
    beta = p.Results.beta;
    
... some code using P,T aswell as alpha and beta ....
end

If you want to add them as parameters, use addParameter like this :

% to use the function as 
% [x,y] = pricingprogramme(P, T, alpha=alpha_value, beta=beta_value)
% or pricingprogramme(P, T, alpha=alpha_value) 
% or pricingprogramme(P, T, beta=beta_value) 
% or pricingprogramme(P, T, beta=beta_value, alpha=alpha_value) 
% or pricingprogramme(P, T)
function [x,y] = pricingprogramme(P,T,varargin)
    p = inputParser;
    addParameter(p,'alpha',10, @isnumeric)
    addParameter(p,'beta',0.1, @isnumeric)
    parse(p,varargin{:})
    alpha = p.Results.alpha;
    beta = p.Results.beta;
    
... some code using P,T aswell as alpha and beta ....
end

NOTE: @isnumeric is to check that the input value is a numeric value

[Benjamin Wilson]

Thank you!

Answer 4

[madhan ravi]

Use nargin() to determine if number of inputs are less than three assign the default values to alpha and beta else feed in the actual values of them

[Benjamin Wilson]

Thank you!