how to not use all input arguments in the function because some of the arguments are fixed?

how to not use all input arguments in the function because some of the arguments are fixed?

[Stephen23]

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html

Answer 1

[DGM]

If you're writing a function and want certain arguments to be optional (with internal defaults), read about varargin

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

From the scope of the function, varargin can be handled as a cell array. How you parse/validate its contents is up to your needs.

I generally assign all the parameters to their default values prior to parsing the inputs, overwriting the defaults as the user-defined values are collected from varargin.

[Alfandias Saurena]

for example, my function (area) just need 1 argument to input (h). in its function require 2 input, (B) and (h). so how to skip parameter (B) because it has been defined before.

B=20;
h=5;
area1=area(h)

Unrecognized function or variable 'B'.

Error in solution>area (line 6)
A=B*h;

function [A]=area(h)
    A=B*h;
end

[DGM]

Unless area() is nested inside another function wherein B is defined, the above definition isn't available to it. It would either need to be explicitly passed to area(), or area() would need to internally define it such that it's a constant or a default for an optionally user-specified parameter.

As I doubt it really makes sense to have a rectangle area function that presumes the size of the rectangle, Steven's suggestion is probably more appropriate.

That said, I'll just offer this for sake of clarification anyway.

area(5,10)

ans = 50

area(5)

ans = 100

function [A] = area(varargin)
% A = area(height,{width})
%  calculate the area of a rectangle
%  if not specified, the width is assumed to be 20
    
    B = 20; % default
    narginchk(1,2);
    switch nargin
        case 1
            h = varargin{1};
        case 2
            h = varargin{1};
            B = varargin{2};
    end
    
    A = B*h;
end

[Alfandias Saurena]

So, B is defined inside the function.

this is another function i created. i define (Qn,S,B,M, and ks) for (rough_secant) function because in (secant) function its only need (y) variabel

clc;
clear all;

y=secant(1,@rough_secant);

function [dQ]=rough_secant(y)
    Qn=84;
    S=0.0005;
    B=20;
    m=0;
    ks=0.006;
    A=luas_penampang(B,m,y);
    P=keliling_basah(B,m,y);
    R=jari2_hidrolis(A,P);
    C=chezy_rough(y,ks);
    V=kecepatan_aliran(C,R,S);
    Qc=V*A;
    dQ=Qn-Qc;
end


function [C]=chezy_rough(y,ks)
    C=18*log10(12*y/ks);
end

function [us]=shear_velocity(R,S)
    us=sqrt(9.81*R*S);
end

function [C]=chezy_smooth(y,vsc,us)
    C=18*log10(12*y/(3.3*vsc/us));
end

function [V]=kecepatan_aliran(C,R,S)
    V=C*sqrt(R*S);
end

function [A]=luas_penampang(B,m,y)
    A=(B+m*y)*y;
end

function [P]=keliling_basah(B,m,y)
    P=B+2*sqrt(m^2+1).*y;
end

function [R]=jari2_hidrolis(A,P)
    R=A/P;
end

function [y]=secant(x,F_x)
dx=0.01;
y=x;
f=F_x(y);
    while abs(f)>0.0000001
        f=F_x(y);
        f1=F_x(y+dx);
        f2=F_x(y-dx);
        f3=(f1-f2)/(2*dx);
        y2=y-f/f3;
        y=y2;
    end
end

Answer 2

[Steven Lord]

You can use an anonymous function "adapter".

f = @(in1, in2) max(in1, in2); % I could have used @max
                               % but I wanted to be explicit
f_2p5 = @(x) f(x, 2.5); % Call f with the first input specified by
                        % the user and the second fixed by me as 2.5
f_2p5(1:5)

ans = 1×5

2.5000 2.5000 3.0000 4.0000 5.0000

f(1:5, 2.5)

ans = 1×5

2.5000 2.5000 3.0000 4.0000 5.0000